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 Post subject: Starter Rebuild Guide: Mitsuba 2-28 (Rebel 250 et al) *
PostPosted: Tue Jul 03, 2007 8:19 pm 
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Joined: Jul 25, 2003
Motorcycle: 98 Valkyrie
Rebel: 250
Country: USA
State/Province: GA
City: Vidalia
Warning!
This is extremely long!


This was originally intended to be a saleable guidebook, and as such it is written to a depth of detail and explanation not generally found on a forum. It will also include a great deal of data that the average forum-browsing wrench will likely already be familiar with. Be aware that it is in there because this was originally intended to be a general-distribution publication, and as such was written for those with low-to-moderate skill levels.

It's purpose as a saleable publication was postponed indefinately pending the inclusion of photographs and diagrams, which I have to this date not had time or circumstance to include. Thus, I have decided to post it here, where it will likely do some good for someone down the line, and I have opted to believe that posting it here will in some way allow me to pay forward one of the many good turns that were done on my behalf over the years. Paying assistance forward is a long-standing biker tradition, and I am happy to find another way in which to again do so.

Again: Warning on the length! It is presented in its current entirety!

I present it in it's entirety for two reasons:

I spent a great time (as in "having fun") and a great deal of time (as in "not having fun doing something else") Doing the rebuilds on which this text is based, as spent several hours upon hours organizing notes, scribbles, stray doodles, and some interesting-looking age spots on my hands into a coherent format. I did not relish the idea that this work would never come to the eyes of the people for which it was intended.

I have no desire at this time to re-re-re-re-re-re-re-re-reedit it. I'm sure I left out some "re"s, and likely you'll spot them. Good for you, and all that. You win a no-prize. It will immediately be sent no-where. :lol:


Another red blurb!

While this work is being offered by the author (me) free of charge, it remains his copyrighted intellectual property. As I have posted it online, I have no qualms about anyone looking it at, even in it's unfinished-yet-likely-final state.

However, NO permission to reproduce this article is implied by its presence here. To obtain permission, ask. Ask right here in this thread, if you want, or by PM.

Duplication or other reproduction of this material will be given to anyone who asks for it, with the following limitations:

Reproduction must be for personal use only, and must include the following blurb:

Originally posted to www.250.com on 7/3/07
Original Copyright 4/23/05 D.E.Oliver
All reproduction forbidden, except from original source and by individualy-granted permission.


No; I'm not a jerk-- like I said, anyone who asks for it will be granted permission. This is just one of those things you have to do to keep other people from making trouble for you down the line.


And just because of everything he's done for us in the past, I would like to go ahead and grant Jack Baumann permission to copy this, if he is so inclined, and a further permission to make multiple copies to give his customers if, again, he is so inclined. The blurb, however, will need to appear somewhere on the copy.

This material will be broken into smaller sections in individual posts so as to make following it, and permitted copying, easier in the future.

The text will begin in the next post.

Thanks for watching!

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Fri Dec 19, 2008 8:42 pm, edited 3 times in total.

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 Post subject:
PostPosted: Tue Jul 03, 2007 8:21 pm 
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Motorcycle: 98 Valkyrie
Rebel: 250
Country: USA
State/Province: GA
City: Vidalia
Inspired by a general how-to I posted on starter rebuilding,

I decided to go ahead and write up a comprehensive guide to rebuilding the specific starter used for the Honda CMX 250. For what it's worth, I have been given to understand that this same starter was used on the CM250 as far back as 1981. I have no way to verify this, but a check of my vendors confirmed that what limited amounts of aftermarket parts available for the starters on these bikes are identical. Granted, the list of parts available aftermarket for motorcycle starters in general is far from comprehensive, so even the similarities of these few parts is not quite confirmation. It is equally possible that this starter fits a number of other Honda machines as well.

In order to ensure that the rebuild process explained here is accurately related, a non-functioning starter from a Honda Rebel CMX 250 and two functioning units were completely torn down to verify details learned from previous rebuilds. While there are many similarities from one model starter to another, there are also some slight variations within different units of the same model number. In any circumstance where variations are known to exist, care has been taken to mention the known variations.

This guide has been divided into sections, each section dedicated to a specific portion of the starter. While the actual repair work may not be done in the same order as presented in this guide, the order was carefully chosen based on the steps of the teardown process. As each portion of the starter is removed, the repairs and tests specific to that portion of the starter are discussed. The end of each section includes any suggestions or techniques that may make the procedure easier or increase the value of the repair.

Also, many sections will include possible "work-arounds" for serious problems. It is noted here, at the front of this guide, that these workarounds are not recommended as proper repair procedures. They are included exclusively as a possible solution to repair the starter, and are included only because many of the parts of this and other motorcycle starters are simply not available from the aftermarket; some are not even sold as separate pieces from Honda themselves. These workarounds may make the difference between saving your starter or having to discard it and order a new one, which can be both expensive and time consuming, often prohibitively so. On a further note from the author, these work-arounds have all been performed by the author and other electrical rebuilders on numerous occasions, but only at the specific request of the customers owning the parts being repaired. Please keep in mind when considering a work-around that they are not recommended procedures, and no guarantee can be given that these techniques will work in every situation. It is not possible to include every potential work-around, and only those workarounds that have demonstrated a better than ninety-percent success rate have been included.

The author would like to take a moment to expressly thank Jack Baumann at Jack's Rebel Warehouse in Sanford Florida for donating the non-functioning (read: "completey burned down") starter used to verify the information in this guide. And by way of further thanks, the rebuilt starter has bent sent back to him, with the author's deepest gratitude. And as a personal message to Jack: Thank you. This starter was perfect for my needs; it needed everything! There are good people; there are great people, and then there's you, Jack: way up above the best.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 9:31 pm, edited 3 times in total.

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 Post subject:
PostPosted: Tue Jul 03, 2007 8:21 pm 
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Joined: Jul 25, 2003
Motorcycle: 98 Valkyrie
Rebel: 250
Country: USA
State/Province: GA
City: Vidalia
Things to have on hand

Like any other repair job, there are a few essential tools to do this job properly. At a bare minimum, this job will require a bench vise, a set of pick tools (similar to dental probes), a hammer-driven impact screwdriver with a #3 Phillips drive bit, and soldering supplies.

Ideally, all of the following tools will be available to complete the project:


Bench vise
Hammer- driven impact screwdriver
#2 and #3 Phillips bits for impact tool
Hammer
Punch
Non-marring hammer
Brass drifts
Straight-tipped lock ring pliers
Penetrating oil
Bushing installation and removal tools
Press, mechanical or hydraulic
#2 and #3 Phillips screwdrivers
Strong soldering iron (not pencil type)
High-temperature solder (high silver content)
Permanent marker
Tap and die set
Lithium grease
Needle-nosed pliers
Magnetic tray (to prevent parts loss)
High temp, high-pressure grease
Cleaning solvent and degreaser
Propane or MAPP gas torch
Steel wool
Point or orifice files
Emory cloth
Sandpaper: 120 grit, 200 grit, 400 grit
Bench lathe
Dremel or similar tool
Insulating varnish
Liquid electrical tape
Polyolefin ("heat shrink") tubing
Electrician's tape
Rebuilder's Insulating Varnish*



While this list is not exhaustive, it should also not be intimidating. The majority of repairs will use very few of these materials. Read the guide completely to get a good understanding of the procedures and gain a better idea of what may or may not be needed for a particular repair.


*A note about Insulating varnish

Insulating varnish is available from electrical rebuilder's specialty vendors. Unfortunately, it is not commonly available from other sources. It is a paint-like gel coating that is used to seal against potential shorts on various electrical components when simple insulation is not appropriate. It is generally available in spray cans (the most convenient way to use it), and should be used carefully. It tends to spray very heavily. When using it, take care not to use it heavily, as this will affect drying time, and may even prevent it from drying properly. Further, excess bulk of the varnish can affect clearance between close-tolerance parts. Insulating varnish is not a paint, and should be applied not in a single coat, but in fine mist coats, building to achieve the desired coverage.

While insulating varnish is preferred for applications requiring it, as noted above, it is not readily available. Because of the supply problem, here is the first work-around:

A lesser substitute is available. Epoxy-based appliance paint can be used in place of insulating varnish. Do not use white, as the color pigments in other colors thicken the paint and increase the insulating properties. Do not use a metallic paint, as the metal flakes will defeat the insulating properties of the paint. Also, be aware that unlike insulating varnish, the epoxy-based appliance paint will dry hard and inflexible, so more caution should be taken to avoid scratching it, which will create potential shorts.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 9:34 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 03, 2007 8:24 pm 
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Joined: Jul 25, 2003
Motorcycle: 98 Valkyrie
Rebel: 250
Country: USA
State/Province: GA
City: Vidalia
Learning a little bit about your starter

After you have removed your starter, take a minute to clean it if necessary. Mild degreaser will work well. Allow it to dry thoroughly and take it in hand to study.

The first thing you will notice, if you're not familiar with starters, is that your starter is composed of three separate sections. There are two aluminum sections-- one on each end-- and a large steel central section. From the "nose" of the starter (the part that fits into the engine), these are properly named the Drive End Frame, Field Case, and Commutator End Frame.

The "ends" of the starter-- the parts made of aluminum-- are called the frames. The front frame-- the one through which the splined shaft protrudes-- is the drive end frame. It is referred to as the drive end frame or just the drive end. It is so named because, for most starters, this is the end from which a Starter Drive Gear or a Starter Clutch is driven.

The other end is the Commutator End Frame, or Commutator End. Both end frames house the parts for which they are named, as well as various bearings, bushings, thrust washers, and other parts.

The center section of the starter (the main cylinder that houses the armature and fields) is called the Field Case. It will be referred to for the rest of this text as either the "field case," the "case," or "that cussed thing that fell on my toe!" For most motorcycle starters, the field case is going to be the only part of the housing that is made of steel. Your field case may or may not have large screws tightened into it; the starter used to write this guide had them. The starter on the author's current Rebel does not. More on these screws shortly.

The two long machine screws that run down opposite sides of the starter are the Through Bolts. The through bolts hold the frames and cases together, and they are used during assembly to adjust the linear orientation of these parts with one another.

Getting into the specifics of your Rebel 250 starter, this starter is a Mitsuba (the most common make of starters on imported motorcycles) and it is a model 2-28. This information is noted on the flat part of the commutator end frame. This is not the complete designation of the number, but more a "series" type number; there are many different Mitsuba starters in this series. They are identified numerically by part numbers (for the complete units) starting with 2-28. Any series starter shares a great deal of commonality with other starters of that same series. In fact, the 2-28 Mitsuba starters are all almost identical except for the end frames that vary from model to model. In a couple of cases, there are differences in the drive end of the armature shaft as well, but the mechanical specifications inside the starter were essentially unchanged.

This starter is rated at .4kw, meaning that it takes 400 amps to produce a magnetic field strong enough to turn this starter at full RPM. This is of course a "no-load" rating (meaning that the starter is secured to a testing bench and not doing any actual work such as turning over the engine); when attached to a starter clutch and an engine, it takes more power for the starter to turn at full RPM.

The starter used for this guide does not use rare-earth permanent field magnets. Rather, it uses an older technology involving electromagnets energized by a series of field coils. Field coil-type starters are easy to identify; they can be identified without opening the starter at all. The Pole Shoes (the steel "blanks" that serve as magnets when the starter is energized) are fastened to inside of the field case (the main cylindrical body of the starter) with large counter-sunk screws. Any starter with screws around the center of the field case is a field coil-type starter. In permanent magnet field case starters, rare earth magnets are affixed to the field case with an epoxy-based adhesive. These magnets are arranged according to polarity, whereas field coil-type starters use long lengths of wire wound in such a way as to produce alternating electromagnetic polarity in the pole shoes when the fields (the wound areas of the wire) are energized.

Mitsuba 2-28 starters are in-line gear reduction starters, meaning that the main shaft of the armature, rather than turning the final drive itself, turns a series of gears. These gears ultimately turn the final drive. The gear-reduction system of starters is so equipped (and most modern starters are gear reduction type) because gear reduction allows an increase in the available torque without requiring a drastic increase in power consumption or the physical size of the starter itself. It accomplishes this by using the gears to "trade" RPM for torque strength.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 9:43 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 8:27 pm 
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Motorcycle: 98 Valkyrie
Rebel: 250
Country: USA
State/Province: GA
City: Vidalia
Disassembly and repair

Before beginning to disassemble the starter, take a very close look at the field case. Look around the edges where the end frames are mounted. All Mitsuba starters include very small alignment marks stamped into the field case. These "ditto marks" align with similar marks or particular ridges on the starter's end frames. The starter must be reassembled with these marks aligned. Not only does this ensure that the brush leads (they are discussed later) are properly positioned inside the starter, it also ensures that the positive stud (where the power wire attaches to the starter) is oriented properly when the starter is assembled and installed on the engine. If the ditto marks cannot be located, or if they are deemed insufficient, they can be augmented. A small punch can be used to make additional marks on the edges of the case and frames, or a permanent marker can be used to simply draw a bold line from one end of the starter to the other. If a punch is used, be sure to use blows only strong enough to mark the case; do not chance deforming the case. Further, use two distinct patterns of punch marks-- one on each end of the case-- to prevent accidentally assembling the starter with the field case installed backwards. If you are uncertain of your ability to mark with a punch and not damage the starter, consider an automatic punch, or perhaps using a dremel or drill to etch shallow marks into the cases.

Care is stressed a lot when disassembling any starter; this is extremely detail-oriented work. There are many pieces and parts that will vary in size and location even among identical units; it is important that they go back together exactly as they came apart.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 9:45 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 03, 2007 8:28 pm 
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Rebel: 250
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City: Vidalia
The Drive End Frame

The drive end frame has a narrow "bottle neck" in the front of it, through which the drive passes. Remove the rubber O-ring seal around the neck. Clean it with non-petroleum degreaser (petroleum-based degreasers can swell and deform the rubber material) and set it aside. Stand the starter up in the vise such that the starter is on end, commutator end on top and the bottle neck of the drive end frame is lightly bound by the vise (do not crush or deform the aluminum frame!) and the weight of the starter is supported by the flat surface of the shoulder. Apply a quality penetrating oil to the threaded ends of the through bolts and allow it to soak for a few minutes.

The bolts are very thin, usually fine-threaded, and they thread into a simple cast aluminum. Any dirt, debris, or oxidation can damage threads, break of the bolt, or ruin the threads in the casting of the drive end frame. The penetrating oil will make removing them significantly easier. Through bolts are too often broken when disassembling motorcycle starters. Do not skip the penetrating oil.

Using a #2 Phillips bit with the impact screwdriver, remove the through-bolts. If for some reason the starter being repaired uses some other type of fastener, then obviously use the appropriate drive socket should be used. If the through bolts are still difficult to remove, try more penetrating oil, or perhaps a small amount of heat from a propane or MAPP gas torch applied to the threaded area of the drive end frame. If heat is used to help loosen the bolts, make sure that the unit cools completely before any attempt is made to handle the starter or disassemble it further.

Once the bolts are removed, make sure that the starter is still secured in the bench vise. Wiggle the field case a bit to see if it will break loose from the drive end frame. If not, using a non-marring hammer (or a steel hammer and non-marring drift of some sort, such as a piece of brass or wood), try to gently separate the field case from the drive end frame. Use light sharp raps of the hammer. IF THE DITTO MARKS HAVE NOT YET BEEN LOCATED OR CREATED, DO SO BEFORE REMOVING THE FIELD CASE!

Very slowly and very carefully remove the field case. Pay particular attention for objects falling from the field case (for this reason, it is best to do the removal while holding the starter closely over a magnetic tray). Nothing should fall out, but something might. If anything does fall out of the starter, try to notice exactly where it came from, and in what order it fell out. (Working over a magnetic tray makes this easier, as it eliminates a great deal of concern over where it landed.) If anything does fall out, it will most likely be either a small gear (a planetary gear) or a large round flat piece of metal (the center plate) or a bronze bushing. Leave them in the tray for inspection later. If any washer-like objects fall from the starter (they will be very thin; these are the Thrust Washers, which are essentially a type of shim), make sure to count them. They are very thin, and often stick together. Make certain of the exact number of thrust washers that fell out. Make a note that these thrust washers were for the drive end and set them aside.

Once the field case has been removed, the inside of the drive end frame is visible, and an outer ring gear (the Stationary Gear) and two smaller gears (the Planetary Gears) can be seen. Before stopping to inspect the drive end, carefully turn the field case over (hold the commutator end securely attached; there is nothing more distracting than having to go chasing a bunch of parts right now) and set it somewhere stable so that no parts will be lost from it. Once the field case has been set aside and secured, turn back to the drive end frame.

If you did not see the gears mentioned above, don't be alarmed. Likely the center plate has remained attached to the drive end frame. It is a thick round piece of metal that separates the workings of the field case from the workings of the drive end. Simply pry it carefully out of the drive end frame with an appropriate pick tool and set it aside. Note closely that it has a small tang moulded to it, and that this tang will fit into a matching notch in the edge of the field case.

If you find a thin, large O-ring, remove it. If you do not find the O-ring on the drive end frame, check the recess around the lip of the field case; it may have remained in place. Penetrating oil or a small amount of automatic transmission fluid can make removing the O-ring easier. A pick tool may be used to carefully dislodge it before attempting to remove it completely. Once it's removed, clean it and set it aside. It is the seal between the field case and the drive end frame, and serves to keep moisture out of the starter. Inspect it for damage and possible replacement.

Once the planetary gears are uncovered, continue.

Examine the planetary gears closely. If they are worn or damaged, or if they are "slopped out" in the center where they ride on the posts of the drive, the starter may have to be discarded. While many of these parts are available aftermarket, the particular parts for the Mitsuba 2-28 are unfortunately not available aftermarket. A salvage yard or compassionate dealer (Man, I crack myself up!) may be able to get them however, so don't give up until all options have been exhausted. But before continuing, find out for sure. If all else fails, see the work-around at the end of this section.

Examine the stationary gear equally well, and for the same reasons. If the planetary gears and the stationary gear are both in good condition, or a source for replacements has been located, continue with the project.


Work-around:

If the planetary gears have worn needle bearings or bushings preventing them from riding smoothly on their mounting posts, it may be possible to find bushings to replace them. You will need to drift out at least one of them and use a micrometer to determine the correct internal and external size, as well as the length of the bushing you will need. Note that the length is really a "minimum length," as a slightly longer bushing can be carefully cut down to work. Oil-impregnated bushings work the best, but beggars can't be choosers.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 9:53 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 8:30 pm 
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Motorcycle: 98 Valkyrie
Rebel: 250
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City: Vidalia
The Drive End Frame, continued

Now look at the inside of the drive end. Remove the planetary gears. Be careful; while most of these gears utilize an oil-impregnated brass bushing, some of them contain needle bearings! After removing the planetary gears, wash out the drive end with a good strong solvent. If your planetary gears use needle bearings, clean them extremely carefully, and pack them full of lithium grease as soon as they've been cleaned. This will help prevent loss of the needles should something happen.

Once the back of the drive (the round plate with the two pins on which the planetary gears were fixed is the actual back of the drive) is clearly visible, proceed.

Turn the drive end over on the vise, such that it is supported by the frame but the drive itself is hanging over empty space. The splined end of the drive should be facing up. Look inside the front of the drive frame, near the base of the splined shaft. There is a small lock ring in there, around the base of the drive's shaft. If it is not visible, clean the frame again. Remove the lock ring.

Give the shaft a spin. If it spins easily, the bearing might not have to be replaced (though, having gone this far into it, there is no reason not to replace it unless removing the drive is proving excessively difficult). If the drive spins roughly, or not at all, the bearing is going to have to be removed. That means removing the shaft.

Soak the shaft liberally with penetrating oil and allow it a few minutes to work. Sometimes a lucky jolt-- simply smacking the drive with a non-marring hammer is enough to dislodge the drive free of the bearing. Most often, however, this is not going to work (but it is always worth a try or two. Be sure to use a non-marring hammer so as not to flare the end of the shaft or damage the splines). If it will not easily jar loose, it will have to be pressed out. If a press is not available, the bench vise can serve as an impromptu press. Take care with fingers and the drive frame. Remember, these frames are not available from the aftermarket! Be sure to support the frame off of the vise's clamping surface; if it is flush to the surface, the drive will have no room to come out of the frame. Do not support the frame by the stationary gear while pressing the drive out! This gear is steel, and is itself pressed into the frame. Forcing it further in will break the frame. Steadily-increasing pressure and liberal use of a good penetrating oil will eventually win out. Be patient.

Sometimes there will be a snapping noise and the drive will then pop readily out. This is not a great thing, but is not always as bad as it can be. If this happens, go ahead and remove the drive. Odds are the bearing is still attached! If it is, look carefully for a spring clip. It is about the thickness of a big paperclip, and roughly triangular. It is perhaps and inch and a quarter across. FIND IT! If the bearing is still in the frame, then the first round has been won. Look again in the rear of the drive end frame (after removing the drive) to see the drive bearing and the clip described above.

The clip rests in a molded groove that surrounds the bearing. It is easily removed with a pick tool by finding one of the ends and simply flipping it out of the groove. A word of advice: cover the clip with one or two shop rags, leaving only the tiniest section visible to work with. This way, should the clip try to fling itself across your shop, you'll likely catch it in the rags before it has a chance to become the reason you threw away a whole entire starter.

Once one end is free of the groove, simply twist the clip out with needle-nosed pliers. Take great care not to deform the clip. Set it aside and turn the drive back over, bottle neck up. Using a bushing driver or a suitable drift, knock or press the bearing out of the frame. The frame is now completely empty except for the stationary gear. The frame can be cleaned, scrubbed, sandblasted, painted (though painting the frame is not recommended), or any other handling required at this point. Unless it is damaged and a suitable replacement has been found, there is no reason to remove then stationary gear. It is hardened steel, and will survive any treatment that the frame itself will tolerate.

If the drive came out with the bearing attached, then one or both of the following things happened:
The groove in the housing broke, allowing the bearing retainer spring to pop loose, thus letting the bearing slip from the housing.
The bearing retainer spring broke or deformed enough to release from the housing, thus allowing the bearing to break free from the housing.

If it was the second one, you may or may not still be able to continue your project. If the spring is merely deformed, there is the chance that it can be re-shaped and re-used. If it is broken, you will either have to secure a replacement (dealer or a salvage yard; though things are a bit grimmer here: salvage yards really don't want to gut an expensive part in order to get a cheaper one, and dealers aren't big on selling starter parts-- anymore, anyway-- when they can sell an entire starter) or reassemble your starter without one. Don't worry; there are ways to make that work.

If the groove itself broke, get the spring and compare it to what remains of the groove. Odds are that it broke out in three places: one where each corner of the spring was formerly located. If there is enough remaining groove to easily reinstall the spring, you have nothing to worry about. The spring just isn't under enough pressure to break that remaining bit on its own; it is only there to prevent the bearing from floating should the outer race ever break free of the frame and spin freely.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:00 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 8:31 pm 
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Rebel: 250
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City: Vidalia
The Drive End Frame, continued



Either open and re-pack the current drive bearing (sealed bearings can be opened; it requires a special pick tool. It looks like a double-curve, and has an extremely pointed tip. Insert the tip carefully under the inner race of the bearing and twist the tool gently to work the point under the shield. Pry the shield up slightly, and then move a bit further down around the race. Continue all the way around the race until the seal is removed. Repeat on the other side. To reinstall the shield, work one portion of the outer edge of the seal under the outer race of the bearing, and continue around its perimeter. After securing the outer edge, work the inner edge back under the race. One word of caution: if you opt to clean and re-pack the current bearing, be extremely frugal with the amount of grease that you use! It never takes as much grease as you think it does the first few times you try this. Overfilling will cause grease to ooze around the seals and get into all sorts of places that it does not belong: into the armature, for example. It helps to remember that you are simply lubricating this bearing, and not packing it as you might do to a tapered bearing.

The new drive bearing can be pressed into the drive frame, or tapped in with a suitable bushing tool. After installing the bearing, install the retaining clip into the groove around the bearing seat and then press the drive back into place and replace the lock ring around the drive's shaft in the front of the frame. Place a small amount of high temperature high pressure grease in the track of the stationary gear. Place some of this grease on the posts for the planetary gears and on the teeth of the gears themselves. Replace the gears onto their posts and set the drive frame aside, planetary gears up. It is finished, and will not be handled again until reassembly.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:03 pm, edited 2 times in total.

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PostPosted: Tue Jul 03, 2007 8:34 pm 
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drive end frame tips

1) Bushings and bearings are available from a number of specialty sources. The inner and outer diameter and overall thickness of the bushing or bearing is required; no application is needed. If the bushings or needle bearings of the planetary gears in your starter are worn out, it may be possible to secure suitable replacements from a specialty supplier. As these parts are not built by Mitsuba but are instead supplied by the lowest bidder, there is too much variance in size to bother including measurements here. To obtain the inside measurement, measure the mounting post with a micrometer. To obtain the outside measurement, press or tap out the bushing or bearing and measure the hole in the planetary gear. Once the bushing or bearing is removed, the thickness can be measured with the micrometer as well. Keep in mind that for this application, bushings or bearings can be used. If a bearing is not available to you, a bushing might be. Good luck.

2) While neither is required, I have developed a pair of things that I like to do when installing the drive bearing. The reason I do these extra things is that if a bearing breaks loose and begins to spin in the frame, it will not only be very noisy, but it will deform the housing, ensuring that it cannot be used again, and because no part of the case is available aftermarket, an otherwise perfectly good starter will have to be discarded.

The first "trick" I learned was to arc the bearing seat in the end frame. I have a number of old batteries and battery chargers lying about the shop. By connecting a ground to the drive end frame and running a positive lead to an old screwdriver or similar implement, I can create an electric arc by touching the probe end of the positive lead to the housing. This leaves a tiny crater and a small bit of steel splattered on the aluminum. By making a quick swipe of the area against which the outer bearing race rides, I can leave a small trail of debris along the aluminum. (it's not as horrific as it sounds; there is very little scarring done at all). This splatter forces tight between the aluminum housing and the bearing race, helping to ensure that a well-used end frame that has seen thousands of heat cycles is still capable of holding tightly to the bearing and preventing it from spinning. Because the splatter also digs into the aluminum under pressure, it cannot exert enough force against the bearing to move it out of center. It will press into the aluminum before it changes the alignment of the bearing.

I won't say that creating open arcs of electricity with an old battery and a screwdriver is particularly safe (or advisable), but it is extremely effective. In fact, I will go ahead and say that creating open arcs of electricity is extremely dangerous, and is not recommended at all. I would also like to note that I have only done this when another frame can't be secured, and the current frame is incapable of holding the bearing securely. And again, it's a bad, bad, bad thing to do. Just so we're clear on that....

The second thing that I learned to do was to paint a very light amount of liquid electrical tape along the leading edge of the bearing's outer race. This helps some with spin-out (not as much as the arcing, in my own experience), but helps considerably with float. By combining the two techniques, retaining springs can be completely eliminated in many cases (though no matter what "additional techniques" you may use, if you do have the retaining spring and it can be put back in place, do so).

Note: Do not elect to forego the retaining spring if you still have it, and if the housing is undamaged. The more protection you have, the better protected you are. Sounds trite, but a lot of people don't think about it like that.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:07 pm, edited 1 time in total.

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workarounds

If you cannot use your bearing retaining spring, you can opt to use one or both of the above methods described in tip #2, or a third one that has worked well for me in extreme cases in the past:
With a Dremel, die grinder, or other thin-kerf cutting tool, score (do not actually "cut") a number of shallow slots in the outer race of the bearing. Rather than making them straight from one side to the other, try to run them on a diagonal. Be sure to score about 1/32 of an inch or less of depth. Place roughly a dozen scores around the perimeter of the bearing. Make similar scores to the section of the end frame that the bearing rides against. Mix up a good two-part epoxy and run a thin layer across the outer surface of the outer bearing race. Press the bearing into the end frame. The epoxy putty should fill the slots you scored in the bearing and in the end frame. Wipe off your excess where it has flowed onto the bearing shield, but any that has bunched on the end frame or bearing race itself should be allowed to remain. If there is enough to run a thin bead of epoxy around the bearing race, mix a tiny bit more and do so. Let it flow onto the end frame and even into any remaining parts of the original retainer spring groove, but be certain to keep it off the shield of the bearing. Set the end frame aside until the epoxy is cured. Please keep in mind that this particular workaround is usually pretty final with regards to replacing the drive bearing. Odds are you're never going to get that bearing out again without destroying that end frame, so if you can, make sure that you install a plastic or rubber-shielded bearing (as opposed to a metal one) simply because the rubber shields are easier to remove without damaging. As long as you can open the shield to clean and regrease the bearing, you likely won't have to worry too much about losing the frame to a permanently-installed bad bearing.

If you are able to do so, re-install the bearing retainer spring, making sure that each corner is tucked securely into the groove.

If you had to use an epoxy putty as outlined above, note the slight shoulder on the shaft portion of the drive. This shoulder is the "stop" that will bump against the inner bearing race, thus positioning it. Pay attention to how much clearance there will be under the gear plate of the drive, and make sure that your epoxy putty is not going to interfere with this clearance. If so, grind the putty down to make enough clearance for the drive.

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"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:12 pm, edited 1 time in total.

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Center plate

Now turn your attention to the rest of the starter. If the center plate fell out during your removal of the drive end frame, examine it now. If the center plate is still in the starter (and in most cases, it will be), take a pick tool and carefully clean out around the perimeter of the center plate. There is a tiny notch in the plate near the edge. This notch is used to hold the center plate in place. There is a matching section of the inner edge of the field case that has been punched and slightly separated so as to form a lock of sorts. Use a hammer and small punch to straighten this locking tab sufficiently to allow the removal of the center plate.

Carefully remove the center plate. If there are thrust washers for the front of the armature, they will usually be located behind the center plate on the Mitsuba 2-28. As you remove the center plate, take care to examine the back of the plate to ensure that there are no thrust washers stuck to the back of it. If there are, carefully remove them and re-install them on the armature shaft for right now to prevent losing them.

The center plate serves two purposes. First, it seals the armature against grease and possible water contamination from the gear chamber of the drive end. Second, it serves to hold an oil-impregnated bronze bushing. This bushing is one of two that hold the armature in alignment between the pole shoes and field coils (or magnets, if your starter is so equipped).

Clean and examine the center plate for cracks or arc scars. Check to see if the bushing moves within the plate. Check the bushing for excessive wear (a micrometer is very helpful here) or damage such as thinning, cracking, or tears. Set the center plate aside, but keep it handy. Once the armature is out, you will need to check the bushing against the armature. For right now, you don't have access to the armature, so set the center plate aside and move on.

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

One end of the armature is now clearly visible, as should be the ends of the field coils (or magnets if your starter has no field coils) and the inside end of the positive lead. Right now, you are most concerned with the thrust washers.

Thrust washers are a variable in starters. They are used to perfect the location of the windings of the armature in the field case. They also serve the secondary purpose of sliding against each other, thus reducing any potential friction against the ends of the bushings. Because mass-production techniques lead to some minor variations in both shaft length and the exact location of the windings on the shaft, shims of varying thickness are usually-- but not always-- needed to precisely position the armature. These shims are called thrust washers. They are generally extremely thin, and are used in varying sizes and numbers as the individual unit requires. While they are generally applied to either one end or the other of the armature, it is not unusual to find that they have been used on both ends. In fact, this is particularly common when a unit uses armatures and field coils of disproportional sizes in order to keep the windings in the ideal location within the magnetic field.

Check your unit for thrust washers on the drive end of the armature. If you have them here, carefully remove them all and identify them as belonging on the front of the armature. I suggest tying them all together with a piece of wire or zip tie or some similar method of ensuring that none of them are lost. While a starter will usually work fine with one tiny thrust washer missing, remember that they are installed for a reason, and that they should go right back in for optimum performance.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:16 pm, edited 1 time in total.

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The Commutator End Frame


Now turn your attention to the commutator end frame. You will notice that there are two small screws through the end of this frame. These screws are used to both ground and secure the brush rack. Remove them, taking care not to strip them! It is difficult to find suitable replacements for these screws. On starters intended for weathered application, such as motorcycles, it is normal to find small O-rings under these screws to help seal out water. If your starter has them, remove them from the end frame (though they tend to remain on the screws).

Carefully tap on the through-bolt mounting ears to dislodge the commutator end frame. Like the drive end frame, there should be a large-diameter thin O-ring seal between this frame and the field case. Using the same techniques applied to the first one, remove this one as well. Take care when removing this end frame, as any thrust washers applied to this end of the armature will be immediately underneath the commutator end frame. They may stick inside the end frame, so be certain to check there before excessively moving it.


In the center of the commutator end frame is a boss that will contain a needle bearing (rare in this day and age) or a bushing (most likely). Inspect it and determine if it will need to be replaced. A micrometer will really help with this, but sometimes the 'stick it on the armature and give it a good shake' method of testing will suffice, especially if you're stranded. I'd recommend the micrometer, of course, but you work with what you have.

Replacing the bushing in the commutator end frame is bit more challenging without a very specific and rather expensive tool. Fortunately for the average do-it-yourselfer, there is an nifty way to solve this dilemma; it requires a set of thread taps. Find the largest thread tap that can be forced into the old bushing. Run it into the old bushing as though trying to thread it. When the tap bottoms out against the commutator frame, do not stop threading. Continue to run the tap. As it cannot go forward, the bushing will give and will ride up the threads of the tap and out of the frame. When installing new bushings, take great care to not deform them. Ideally, a bushing drift set will be available, but this is not something that most home mechanics keep handy. Find a suitable flat-ended drift and rather than using a hammer to drive the bushings in, use the vise to steadily press them in.

Be warned that the thread tap method of bushing removal is a USE AT YOUR OWN RISK method. In about one-tenth of my own experiences, when working with an aluminum end frame, the thread tap will eat through the end of the end frame.

There must be no openings here, as moisture and dust will be able to enter the bushing, causing no end of problems. Further, there is an admittedly minor chance that poking a hole through the center of the frame may alter the alignment of the bushing boss, rendering the starter useless.

If you do opt to use this method and have the misfortune to bore a hole through the end frame, JB Weld, Liquid Steel, or suitable epoxy may help to seal the hole.

The Brush Rack

Now you can see the brush rack. In most cases, this is where you will find the first signs of damage with the starter. But for now, turn your attention to the bushing inside the commutator end frame and examine it as you did the center plate bushing. Also, inspect the aluminum of the frame for heat damage, particularly in the area at the center of the bushing. This can indicate an armature shaft that has slid inside the windings enough to contact the aluminum. This condition must be corrected. Clean the frame thoroughly and set it aside for now. Double check the top of the armature (still in the field case) for thrust washers. Any thrust washers you find should be marked as being for the commutator end and set aside together.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:19 pm, edited 2 times in total.

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The Brush Rack


Before removing the brush rack, take a moment to examine it. The Mitsuba 2-28 starter uses a very simple two-brush set-up. One of these brushes is the negative and one is the positive. The brushes themselves are chunks of carbon formed on the ends of braided copper leads.

If you have ever had to rap on your starter or perhaps put the bike in gear and rock it back and forth against the gear box to get the starter to work, odds are that the brush rack is where your problem is. In fact, the odds are that there are no appreciable remnants of the brushes. The tapping action (or jarring the commutator via the transmission and starter drive) will jar the brush leads to briefly contact the commutator of the armature and create a temporary short circuit that will power the armature. It also tends to arc the commutator considerably, and the typically lower amperage of this poor connection will cause a heat build-up that can remove solder from the commutator bars or cause scaring and pits on the bars themselves. Extreme damage of this type cannot be repaired, and the armature will have to be discarded. As this armature is not available aftermarket, and that means that the starter is essentially ruined and beyond repair. For that reason, you should never tap on a starter to get it to work outside of the one time it takes to get the bike home from wherever the starter failed!

The end of the negative brush lead is spot welded (or soldered, on cheaper after-market units or low-quality repairs) to the rack itself. The screws that fasten the rack to the commutator end frame allow the brush to ground through the frame to the starter mounting screws and ultimately to the engine case. The end of the positive lead is screwed (on original units, it is attached with a #2 Phillips screw) to an insulated copper lead from the field coils on field-coil type starters. On Magnet type starters, the positive lead will run directly to the stud onto which the power wire for the starter is attached.

When power comes in through the positive lead, it travels through the field coils (and in the process magnetizes the pole shoes) and then through the lead to the positive brush, where it passes into the armature through the commutator and energizes the armature (magnetizing it as well). The interaction of the two magnetic fields provide the force to turn the armature and thus the drive and ultimately the engine. If the ground is poor, then enough power cannot be drawn to create fields of sufficient strength.

Look at the brushes closely. Notice that they are held in place by two U-shaped metal frames. There is a spring on the rear of each brush, and this spring keeps the brush tight to the commutator. There is a slot cut into the side of each brush bracket. This slot allows the brush lead and spring to follow the brush as the brush wears shorter and the spring pushes it forward. If the spring is more than half way though the length of the slot (while the brush rack is installed around the armature), the brushes will have to be replaced. Of course, you may opt to replace them anyway.

There may be a small dimple or pin in the field case that serves to align the brush rack. Note how the brush rack orients with regards to it. Not all the field cases will have such indicators, so be careful to note how the rack orients with regard to the positive brush lead of the field coils. If you can't remember how it was oriented when you are ready to reassemble and there is no device on the edge of the case to help you, don't worry. There is a way to determine orientation later; it will be covered in the reassembly instructions.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:26 pm, edited 1 time in total.

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The Brush Rack, continued

Remove the screw that attaches the positive brush lead to the field coil lead and carefully remove the brush rack. Before removing it, note completely the location and orientation of the springs, as they may shift during removal or installation of the rack, and they will have to be properly positioned to perform correctly. Once you have the rack removed, clean it (being careful of the springs) and inspect it. Look for pitting, burns, scarring, and other signs of damage. Notice that the positive brush bracket is mounted on top of a composite insulator. Inspect this insulator for cracks or chips and make sure that the rivets holding the brackets are secure. Make sure that the brushes slide easily through the brackets without hanging or sticking. If needed, use a small file or similar tool to clean the inner surfaces of the brackets. Do not deform them, or they will bind against the brush.

Underneath the brush rack, inside the field case, there should be a paper gasket of sorts. It is not present in all starters, and often lost during previous rebuilds. However, it serves a valuable purpose, so do your best to not damage it if your starter has one.

It has a large hole through which the commutator passes. This gasket is less common on newer units (I do not know why) and is often missing from older units that have been repaired before. Remove it. Be careful, just to stay in the habit, but odds are you will not be able to remove it without destroying it. If you do damage it, you can readily make a new one from gasket paper or heavy cardstock. This gasket serves to catch brush dust as the brushes wear and to help keep it from filtering down into the fields where it can cause a short. However, some brush dust will get through, as the gasket can't touch the commutator lest it get shredded.

Check the brushes themselves for cracks, pits, or softening. If they are cracked or are missing chunks or are too short (as determined above), replace them. They may be flared a bit from wear but otherwise serviceable. If this is the case, lightly file the flares off so that they will pass easily through the brackets.

Generally, it is easier to replace the entire brush rack than it is to repair it or to replace just the brushes. However, you may opt to keep the original rack. If it is damaged, you will have to repair the damage. The very first thing that you want to do is to remove all the rust or corrosion from the rack. The more rust there is, the faster it will continue to eat away at the rack. Some pitting will not matter too much, but remove all the rust.

If the insulator under the positive brush bracket is chipped, inspect the area to see if it is vital to repair. If no metal is exposed, then there is no major concern. If it is possible that the positive brush lead or brush itself could contact the raw metal of the brush rack (and keep in mind that as the brushes wear, the carbon-- which is still conductive even as dust-- will build up in places like this), then the simplest repair is to paint over the area with a product such as Liquid Electrical Tape or Liquid Vinyl. There are also specific insulating varnishes available from specialty shops, but the liquid tape is available almost everywhere auto supplies are sold, and can be built up with repeated applications. Remove any that spills over onto the surface of the insulator, as it can impede the movement of the brushes. If the insulator is cracked but not missing any chips, paint the entire insulator with a light coat of liquid tape or insulating varnish. When the tape dries, lightly sand off the surface of the insulator. Do this also if you have used a tacky type insulating varnish.

If you do not have access to insulating varnish, an epoxy-based appliance paint (in spray cans at most hardware stores) will work almost as well in most applications. Do not use silver or any color containing metallics. Plain white will work, but paints with a heavier pigment-- even just beige-- will work better with fewer applications. And for what it's worth, red is the traditional color for insulating varnish.

Once the rack itself has been determined to be sturdy enough to reuse and the insulator has been found to suitably insulate, examine the rivets that hold the insulator and the brackets in place. If they are loose, they can contribute to premature brush wear or move in such a fashion as to bind the brush, thus preventing it from making good contact. And if they become loose enough to fall out of the rack, they can cause shorts or extensive physical damage inside the starter. The rivets are easy enough to re-tighten: simply place the base of the brush rack against a solid surface (such as your vise or a hammer cheek) and using a hard drift, deliver sharp blows to mushroom the rivets until they tighten up against the rack. Do this only enough to tighten them; don't risk deforming the brackets or breaking the insulator.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:32 pm, edited 1 time in total.

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The Brush Rack, continued

If the brushes are to be replaced, the old brush leads will have to be ground off of the brush rack. Be careful not to damage the actual rack. Clean the exposed surface in preparation to spot weld the leads for the new brushes. Many aftermarket brush racks will feature leads that are simply soldered to the rack. These can be removed by heating them with a solder tool until the solder melts and releases. Clean the area to apply the new leads as above.

Not everyone will have access to a low-temp spot welder (often called a "hot spotter"). For those people, there are still some options. If the brush leads are securely welded to the rack, it is possible to take advantage of this. Cut the old brush leads so that roughly 3/8 inch or so lead is left attached to the rack. Slightly unravel the loose end by gently massaging the weave of the wire open. Massage the end of the new brush lead open, and carefully weave the ends of these leads together. Solder these leads together securely with a high temperature solder, preferably one with some silver content. If you opt to use this method, keep in mind that the brush leads must be bent in such a fashion as to not touch the commutator end frame when installed! The solder will drink into the lead, making it less flexible, so use caution when doing this. Also keep in mind that the lead for the positive brush must be insulated; do not discard the insulation, no matter how much easier it seems to make the job!

Another option for those without access to a hot spot welder is directly soldering the brush leads to the brush rack. As done on many lesser-expensive brush racks, this method works poorly, as the heat generated by the starter is often sufficient enough to soften the solder. Obviously, this can cause the brush to come loose from the rack. However, the strength of the joint can be increased by one of two methods:

The first method is to cut a notch into the brush rack at the mounting location just sufficient enough to allow the brush lead to be forced into the notch. Flare the brush lead a bit on both sides of the notch and firmly solder the lead on both sides. The second method is similar, but involves drilling a small hole and forcing the tip of the brush lead through it. Again, solder securely. These methods are superior to simple surface solder simply because there is a firm physical connection to hold the brush lead even if the solder was to soften. The solder on the brush rack will rarely get hot enough to actually run from the connection, and will usually re-solder the joint when it cools. Again, the solder is only going to come loose in extreme conditions (such as excessive cranking with a hard-start condition), but there is no way to predict when your starter will encounter those conditions. It is better to get the best possible connection than to simply hope against the odds.

Once your brush rack is ready to use, set it aside.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:35 pm, edited 1 time in total.

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Removing the Armature


Now it is time to address the field case itself. Electrically, this is the most active part of the starter. Everything that gets energized is still inside the field case.

Turn your attention to the Field case.

The armature for the Mitsuba 2-28 is removed by pushing it through from the commutator end and out the drive end. To prepare to remove the armature, make sure that the leads from coil to coil are pushed as out of the way as possible. Generally, they will drag lightly on the armature. There is not a lot that can be done about that, but be prepared to have to work them a bit with a pick tool or suitable probe while you push out the armature. Do not push them to the point that they touch the field case itself or the pole shoes. If they do not rebound (and copper is not known for its springiness), they can short out and ruin all your work. You will need to be sure that the single lead coming up to the positive post is clear of the armature as well. Take care to not damage the insulation on these leads.

Once the armature is removed, clean it and let it dry thoroughly. While you have it in your hands, check the fit of the center plate bushing on the armature for excessive slop or wear. It should fit easily, but not wobble or slop. A micrometer will really tell you what you want to know, but as a general rule of thumb, if you can't slop it at all from side to side, and it doesn't bind, then likely you can run the bushing again if you have no other choice.

The bushing in the center plate, should it need to be replaced, can be pressed out or knocked out with a hammer and the appropriate punch or drift. Take care to support the center plate in such as fashion that removing and reinstalling the new bushing do not damage or deform the plate itself. Once you're satisfied with the center plate, apply a light amount of lithium grease to the inside of the bushing and set the plate aside.

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Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


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Inspect the armature for obvious damage such as discoloration to the copper, missing bars, or bars that have come loose and twisted up off the commutator.

If any bars are twisted away from the commutator, you will have to reshape them into place. Heating them to the glowing point with a precisely-trimmed propane or MAPP gas torch can help.

Use EXTREME caution! Too much heat can damage the insulator on which the commutator bars are mounted, and can remove solder from other points of the commutator!

Once the bars are all in place, continue on.

Once the armature is completely clean and dry, check it for shorts. Using an Ohm meter, check for continuity from the copper bars of the commutator to the steel stacks of the windings and the shaft itself. There should be absolutely no continuity from the commutator to any other part of the armature, in particular the stacks or the armature shaft itself.

The shaft is easily recognizable. The Stacks are the laminated steel section through which the windings are wold. This is the steel mass against which the magnet field acts to produce rotational motion.

If there is continuity from the commutator to anywhere that is not the commutator, examine the armature closely to find the cause.

Test the commutator itself. Using the meter, touch one bar on the commutator and check it for continuity to each and every other bar on the commutator. You must have continuity to each bar. If you do, then by default you will have continuity from any one bar to any other. As the brush touches each bar, there must be a pathway all the way through the armature to the bar that is touching the ground brush. And as the armature spins, each bar will in turn serve as both positive and negative conductors. If no bars show continuity to the bar you started with, move around the armature a few degrees and start with another bar.

Any bar that does not show continuity to the first bar should be clearly marked as needing further inspection-- a Sharpie works very well for this.

Examine any bars that do not show continuity. In particular, inspect the stakes. The stakes are the ends of the commutator bars. They are notched slightly and the ends of the windings are both crimped ("staked") and soldered into the notches. The most typical damage here is referred to as a "slung bar," a condition in which one or more bars has gotten hot enough (usually do to a continuous low-amperage or low voltage supply to the armature) to melt the solder from the stake; the motion of the armature will fling the liquid solder from the stake. Not all of the solder has to be removed to sufficiently reduce continuity.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:40 pm, edited 1 time in total.

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Armature, continued


Examine the stacks for deep gouges, scratches, 'polished' areas, or other signs that the armature has been coming in contact with the pole shoes or magnets.

Such signs are clear evidence that the armature is not properly centered. Generally, this is because one of more bushing or bearing is worn out-- usually either the Center Plate bushing or the Commutator End Frame bushing, or both. Less likely, but not impossible, is the possibility that the armature is bent. If the armature is bent, you will not be able to proceed, as this part is not available aftermarket. Of course, if you've been hoarding old starters (as many rebuilders do), you may have an acceptable replacement on hand.

If the stacks show no sign of 'dragging,' then allow the commutator to cool (if you've had to heat it) and examine it again:

To repair a slung bar, use a very small file,such as a points file or orifice file, to clean the inside of the stake and the end of the winding lead. Push the lead firmly into the stake (if needed; often the leads do not move out of the stakes). Re-stake the connection. To do this, you will need a small chisel or punch. Deliver a sharp blow to each side of the stake, moving it to crimp around the lead. Do this only once per side or you risk weakening the stakes on either side of this one or deforming one or more commutator bars. Do not deliver a crushing blow, but make it count. Once you have staked the lead, solder the joint securely with high-temperature solder. Again, a high silver content yields the most enduring results here. In general, a pencil-type solder tool is simply not enough to generate the heat needed for this job: both the lead and the bar should be hot enough to draw a substantial amount of solder very quickly. Some smaller gun-type soldering irons will not do this job either. If you have nothing else available, a propane or MAPP gas torch with a small tight flame will work, but be careful not to weaken the adjacent connections or discolor the copper (discolored copper will not take solder well). Take great care not to use too much solder, or you may create a bridge from the stake to the stack of the windings, thus shorting the armature.

After all the slung bars are repaired, check the bars for continuity again. If there are still bars with no continuity, check the stakes for those bars; it is possible that the solder joint is porous or that the stake was not cleaned sufficiently for the solder to adhere. If the stakes are fine but there is no continuity, trace the winding lead as best as possible by eye looking for a break in the winding. If you find one, you may be in trouble. It is rare that you can repair such a break, but in case you have a break that you can get to, about the only option you have is to try to solder it together.

Remember that the windings are coated with a thin clear insulating varnish and that the coating will have to be carefully scraped off in order to get the solder to stick. If possible, the joint can be strengthened by adding a short piece of similar wire along the joint and soldering it next to the joint. Re-insulate with your varnish, epoxy paint, or liquid tape (listed in order of preference). Keep in mind that the odds of being able to access a break in the winding enough to repair it, but if you get lucky, you now have an option.

If any bars are broken or deeply pitted, you will need to completely clean out the pits and raw edges. Use your high-temperature solder to fill in breaks and pits.

If you have completed all the repairs that you can manage to your commutator and windings but find that you still have one or two bars to which you cannot get continuity, there is one final option. However, it should be mentioned up-front that this is not recommended, and cannot be guaranteed to last, though it has worked extremely well in many cases. If it were possible to simply buy a replacement armature from the aftermarket, this option would not be mentioned at all. But since replacements are not readily available, this option is detailed as a possible method to save your starter.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:42 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:22 pm 
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Armature, continued

You will need to clean all your stakes and bars for this to work. Then you will need to use solder to bridge the stakes for the non-responsive bars to the stakes on either side. Then you will need to bridge those stakes to the stakes on the adjacent bars. This allows the brushes to deliver a charge to the armature windings through the leads for the adjacent bars but will not result in one or two leads being excessively over worked or overheated. Be sure to use a pick tool to cut into the commutator's insulator (that hard "not quite ceramic, not quite plastic" stuff," properly called "mica")) and remove a small amount of the insulation from between the bars to be fused. This will allow a place for the solder to lay.

This is a tedious job, as mica abhors solder, and will resist the attempt to bridge the space between bars. Liberal use of solder flux will help this some, but ultimately, you're going to exhaust the more profane bits of your vocabulary before getting it to work.

Again, this is not recommended, as it will result in a momentary weakening of the magnetic field every time one of these bars is being used. Further, this method should not be used to repair more than two bars under any circumstances. The field will remain too weak for too long a period. Even though the engine may start, the reduced speed of the starter will result in extensive heat build up within the starter, resulting in a very-short lived starter and possible damage to the battery or charging system. For the record, this method has been used at the request of various customers to repair as many as four "wasted" bars, and some of these units have been in use for several years since the repair.

NOTE: if you opt to bridge bars, make sure that your final set of grouped bars can at no time touch both a positive and a negative brush. This will result in a dead short that will cook your battery in record time.

When you are done with all the repair work to the armature, test again for continuity. When there is continuity to all bars, it is time to turn the commutator.

Turning or "truing" the commutator is reshaping the commutator to a more perfectly rounded shape and a more straight-sided profile. This is to ensure more consistent contact with the brush and reduce brush wear. Generally, this is done on a lathe, but not many home shops include lathes. Of course, some people can do amazing things with power drills, but that often includes hurting themselves pretty badly. For the average do-it-yourselfer, a lot of handwork with sandpaper or emory cloth is the best option. Do not use wire-wheels or grinders or flat sanders, as these will generally result in numerous flat spots and gouges in the commutator, conditions that are worse than a worn commutator. Sand the commutator until the bars are showing fresh clean copper and any repair work is completely flush with bars themselves.

Keeping in mind that this guide is written with the do-it-yourselfer in mind, it should be pointed out that while ideally the commutator will be restored to a perfectly cylindrical shape, this is not always possible without a great deal of specialized tools and equipment. However, perfection is only the ideal, it is not critical. As long as the commutator is perfectly clean, reasonably well-shaped, and any soldered repairs are perfectly flush with the copper adjacent to them, it will work fine. The brush springs will help to ensure good contact between the brushes and a slightly-eccentric commutator. Do not excessively waste the material of the bars to get the commutator perfectly shaped; they can only lose so much material (roughly one-third to one-half their original thickness) before they are no longer capable of performing properly. At that point, the armature and, as the armature is not available from the aftermarket, the starter will have to be discarded.

Once the commutator is trued, examine the bars, paying particular attention to the spaces between the bars. Ideally, the spaces between the bars should be recessed between the copper bars. It is interesting to note that while Honda's technical specifications state that any commutator that has worn flush with the mica that fills the spaces must be discarded, Mitsuba's technical specifications do not. In fact, Mitsuba's technical specifications make no mention of acceptable tolerances for the bars of the commutator. Honda, in their statement, and Mitsuba, through omission, are both correct:

As stated above, ideally the bars will present a surface raised above the mica that is used to insulate the bars from one another. And the specifications on most any starter can be used to deduce the same guideline. But again, there are some work-arounds that will be mentioned. And as mentioned above with the comments on bridging shorted bars, these work-arounds are not proper repair techniques, and are only offered here because the armature is not available as a separate part and a person willing to go to extreme lengths may be able to save himself from having to discard his entire starter.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:51 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:25 pm 
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Armature, continued


The commutator ( the "business end" of the armature) is composed of three basic sections. By now, you are very familiar with the bars. The core of the commutator (or simply "com") is an inert insulating material, usually a heat-resistant nylon, or Bakelite-type material or some similar material. In many cases, the material may be brittle, so be careful of sharp or abrasive tools when working with the commutator. The third portion of the commutator is mica. The mica is used, as stated, to provide an insulator between the bars and to help shield the inert filler material of the com from excessive heat generated during the operation of the starter. The bars are set into the mica and wrapped around whatever plastic is used to shape the commutator.

The reason that commutators whose bars have worn to the level of the mica should be discarded has not so much to do with the bars themselves and it does with the brushes. Brushes making contact with the mica will wear substantially faster than brushes that contact only the copper. If the copper bars wear below the level of the mica (and the copper will wear faster than will the mica), contact between the brush and the bars will be sporadic at best, and result in a great deal of arcing and, in very short order, the ruination of the armature.

If you find that the bars are worn very close to the mica, you may wish to measure the depth to the mica from the presented surface of the bars. If the distance is one-thirty-second of an inch or greater, odds are there is nothing to worry about. While the copper will wear with use, generally one-sixteenth of an inch is enough copper to wear the brushes completely out before the copper wears to the level of the mica. If you find less than one-sixteenth of an inch, what you do is entirely up to you. You should be reminded again that at this point, a commutator is usually replaced.

If you opt not to replace the commutator or the complete armature-- and with the difficulty in obtaining replacement parts, you may well decide to try to run the armature as it is-- you have two options. Your first option is to run the armature "as is," so long as the mica is no more than level with the copper of the bars. Simply set the armature aside and move on to the field case. Your second option is to reduce the amount of mica. This may be done with patient and careful scraping away of the mica with a pick tool or abrading it away with a very small file. Take care to not wear away the bars. The edges of the bars should always be as sharply defined as possible. Another option is to use a Dremel or similar thin-kerf cutting tool to carefully grind out a small amount of mica. Be careful not to take out too much of the mica; it does act as an insulator, after all. Getting the mica down to one-thirty-second of an inch below the level of the bars is generally sufficient. If the level of the mica is higher than that of the bars, grind it away until either you get the clearance that you need or you remove all the mica. If you remove all the mica, the commutator is no longer useable, but at the point that the bars are worn below the mica, the commutator is not properly serviceable; at this point, you have nothing to lose by trying.

_________________

Duke
"Skills must be Learned"
------ Herb Christian


"Ask your doctor if medical advice from a television commercial is right for _you_."


Last edited by Duke on Mon Jun 21, 2010 10:56 pm, edited 1 time in total.

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