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PostPosted: Tue Jul 03, 2007 9:26 pm 
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The Field Case


Set the armature aside and pick up the field case again. Inside the field case are located the four pole shoes (metal blanks shaped to conform to the curvature of the case itself) and the field coils (wrapped around the pole shoes). Also visible (at the drive frame end of the case) is the base of the positive stud and the solder joint that attaches it to the field coils. First, look at the outside of the field case near the base of the positive stud. If you have not removed the nuts and insulators from the stud, carefully do so now. Look closely (a flashlight will help) at the base of the stud where it passes through the field case. There should be one (sometimes more, if the starter has been repaired here before) O-ring seals that serve to both center the stud in the hole and insulate it from the field case itself. If this seal is missing, replace it. Suitable O-rings can be found at most auto parts supply stores. Ideally, the O-ring will protrude just slightly above the surface of the field case when installed. It may be necessary to stack two or three O-rings to get the desired thickness; the stud must be insulated from the field case. Once the stud is properly insulated, check the inside of the field case.

Start with the base of the stud and its soldered connection to the field leads. The base of the stud has a recessed groove cut into it, and a copper strap from the field coils fits perfectly into this groove. Ensure that the connection is sound and that the strap is undamaged, well-insulated, and not touching the side of the case. Examine the insulation around the field coils (usually made by wrapping a special "coil wrap" paper around the field coils themselves) for obvious breaks, tears, or signs of burn-through. On the commutator end of the field case, inspect the lead that powers the positive brush for any signs of damage or failure.

Once you have completed your visual inspection, the field case should be tested for shorts. This is done simply by checking for continuity from various points of the field case. First, check continuity from positive stud to the field case itself. Then check continuity between the positive stud and the pole shoes and again from the positive stud to the pole shoe screws. There should be no continuity whatsoever for these three tests. Test from these same locations to the positive brush lead. There should be continuity only between the positive post and the positive brush lead. All other locations should show no continuity. If you show continuity between any pair of points other than the positive stud and the positive brush lead, the field coils will have to be replaced (and again, they are not available aftermarket) or repaired. If you do not show continuity from the positive brush lead to the positive stud, the field coils will have to be repaired.

Depending on the materials and coatings used in the assembly of your starter (and this will vary from unit to unit), you may not show continuity from the case to the pole shoes or screws, or even from the pole shoes to the pole shoe mounting screws. While you will normally get at least some small continuity, do not be alarmed if you don't.

This next step makes a critical difference in the performance of the re-assembled starter. Be extremely careful to make the suggested marks. While the starter will operate if you elect not to do so, or if you lose you place, it will get optimum performance if you take to heart the following suggestions.

As explained above, the field coils and pole shoes are two parts of what it essentially an electromagnet. The pole shoes are made of steel specifically so that they can be magnetized. However, like any other steel object, repeated exposure to magnetic fields will eventually leave them magnetized, even though the strength of the magnetism might be miniscule. Obviously, the age of the starter and the frequency of use are the major contributing factors to the strength of any magnetism the pole shoes may posses. Like any magnet, the pole shoes, when energized, will have a definite north and south polarity at each end. To further complicate things, when the field coils are energized, two of the magnets become exclusively "north" magnets in opposition to the "south" magnets on either side of them. It is the interaction of these fields, and similar fields within the windings of the armature (each of the laminated steel bars that composes the major mass of the armature will become alternately north or south magnets when the armature is energized) that causes the armature to spin.

When the pole shoes are removed and replaced randomly, they may end up in a position opposite to what they have been previously. While any amount of magnetism they may have come to posses may be very small, it is an opposite force and will weaken the effect of the electromagnetic field. While this is generally inconsequential, pole shoes that have developed a powerful magnetic strength can potentially reduce the armature speed drastically until they have taken to their new charge. In most cases, the pole shoes will have no detectable magnetic strength, but it is easier to take precautions in every case than it is to tear apart one starter in a hundred to try to figure out the ideal location and orientation for each pole shoe, particularly as you may have to do it more than once.

Before removing the pole shoes, clean them so that they can be easily marked (again, a Sharpie works really well for this). Number the pole shoes one through four, and mark a corresponding number on the field case (inside or out; your decision. But make sure that the mark is in no danger of being accidentally removed). Also mark the pole shoes to indicate their orientation in their position. This can be immediately important on some starters simply because the pole shoes have different shaped flanges from one end to the other. The Mitsuba 2-28 is not one of those starters; its pole shoes are symmetrical in every direction.

Once you have marked the pole shoes, you are ready to remove them. Using the impact screwdriver and a #3 Phillips bit, loosen the pole shoe mounting screws. You may find it helpful to take a pick tool and clean and debris from the screw head first in order to assure a good fit with the bit. Remove the pole shoes one at a time, always taking great care not to damage the insulating paper on the coils. If they are rusty or greasy, clean them. Make sure to remove all rust from the pole shoes. Be careful to note the location number and orientation marks of each pole shoe; if you should clean the marks off, remark them before you forget.

Removing the field coils is patient work. First, remove the insulating O-ring from the positive stud. Taking care not to damage the coil paper, peel the coils off the side of the field case. They are not actually glued in place during assembly, but age, grime, and even surface rust of the case will act to bond them firmly. Once the are worked away from the case, carefully press the positive stud through the hole in the field case. Gently remove the field coils. Do not attempt to flatten them or straighten them out unless it is absolutely necessary to affect a repair. The coils are each a single length of soft, flat copper wound tightly into shape. Excessive bending will weaken them, and can break them. With the coils removed, lay them on a piece of wood or other insulated surface and again test them for continuity from the positive stud to the positive brush lead. If they fail to have continuity between these two points (the two ends of the windings of the coils), test them in smaller sections.

Between each coil is a single thick bridging lead, the soldered (or hot spot welded, depending on the age of the unit and the line it was assembled on) ends of which are generally not insulated (again, on some units, the entire lead may be without insulation). Test for continuity from the positive stud to the nearest end of the nearest bridging lead. Continue to test from the stud to the next furthest available point until the unit fails to show continuity. This will help to isolate the location of the short. Do similar testing from the other end the positive brush lead to determine if there are further shorts in the field coils. Shorts can be located anywhere in the field coils, and what with them being wrapped in paper, they can be difficult to pinpoint. Often, tell-tale signs such as burnt or torn paper will give their location away. Excessive rust clinging to one or more parts of the coils can also indicate a potential short, as the moisture which causes the rust can soak the paper and allow the coils to ground against the field case, thus causing arcs.

In most cases, a short in the continuity of the field coils is going to occur in one of the bridging leads. Repeated use of old or weak batteries forces the starter to run on lower than ideal voltage and amperage, as will a charging system incapable of imparting an ideal charge to the battery. This results in excessive heat build up in the energized circuits of the starter, as they remain energized much longer in order to cause the reactions needed to start the engine. An engine with a hard-to-start condition amplifies this problem greatly, as the starter will be used for greater than normal lengths of time, and will often serve more closely-grouped duty cycles than would a starter on an easily-fired engine. There is no allowance for cooling the starter, as it is not intended to run more than a few seconds at a time, and in general use there is plenty of time for the starter to cool down before it is called on to work again. It is this heat build up that most often causes the loss of continuity in the field coils. The soldered connections of the bridging leads are generally the first part of the field coils to fail from excessive heat.

_________________

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 11:00 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:28 pm 
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Field Case, continued


The most common failure point is the connection to the positive stud. As noted earlier, the back of the positive stud has a groove cut into it and the bridging strap that feeds the coils is soldered into it. Examine this connection closely. Ideally, it should be difficult to detect the groove, as it is filled by the strap and the hollows under and beside it should be filled with solder; there may even be a thin tinning of solder across the back of the strap, smoothing out the entire joint. Even if you found good continuity to a point beyond this lead, examine it closely for signs of potential failure, such as melted out solder or small black arcs near the edge of the stud or the lead. If this joint is fine, then look further down the lead (the insulation, if present, is a cloth fiber, and should readily move and even open slightly, making this inspection possible.

While there are certain points that should be insulated, if only as a precaution against further starter failure, it is not unusual to find that some of this insulation has either been omitted, been removed by previous repair procedures, or has simply gone missing as a side effect of damage. Before replacing the coils in the case, these areas should be insulated. The bridging straps in particular, while they generally can't be fully insulated, should be insulated as much as is possible. If a lead has come loose, it is easy to insulate with polyolefin tubing (commercially available as "heat shrink tubing"). Do not detach a lead in order to so insulate it; instead, use another form of insulation. A carefully and tightly applied single layer of electrician's tape is better than nothing. Avoid using the liquid tape preparations, as it is difficult to determine good coverage without using excessive bulk (though liquid tape does have its uses for the coils).

Examine the joints for all the bridging straps to ensure that none of them have failed or show signs of impending failure. If any strap needs to be repaired, including the lead to the positive stud, then clean the area to be repaired and solder it together. In many cases, this will require breaking the current connection, but it is vital that the connections be perfect. While a pencil-type soldering tool will most likely be ineffective to make these repairs, when working with the field coils it is preferable to using a torch. The wide-spread heat and flame of a torch will damage the insulating paper of the coils. The field coils are lightly coated with the same insulating varnish that the mica in the armature is coated with. Because of this, the areas to be soldered will have to be thoroughly abraded or they will not take solder. Remember that to get the best connections, both pieces being connected should be heated and tinned (tinning is a process whereby a piece to be soldered is first cleaned, heated, then covered in a thin coating of solder. When two pieces so coated are heated together, the joint is stronger than attempting to flow solder onto the pieces.), and while they are being heated and joined together, an extra small amount of solder should be added to the joint. This will slightly raise the amount of heat needed to break the connection, as well as provide a safety net of sorts should the connection become hot enough to partially liquefy the solder.

Often, a shorted strap lead will have lost enough mass to make it impossible to reconnect. In these cases, new material will have to be found. While the ideal is to replace the field coils, as with so many other parts for this starter, there are no spares available from the aftermarket. And for that reason alone, the following suggestions are offered:

Short pieces of strap may be cut from other field coils, if available (the field coils from a Ford Pinto starter are almost perfect), or may be cut from tubing of sufficient thickness and then beaten and ground into shape. If hollow tubing must be used (and with any luck it won't have to be), then be sure to fully flatten it and shape it for its intended purpose. Once it has been made to the desired shape and size (and thickness is critical for clearance issues), heat it with a torch and fill it as best as possible with the solder. This will help to keep it in shape, and help to prevent internal arcing that may lead to burn-through and ultimately further shorting. If your torch can be made hot enough to greatly soften the tubing, it can often be forged into a solid piece with liberal use of a hammer, and then reshaped. Wire should be used only as an absolute last resort, simply because it takes a substantial gauge of wire to carry the same current as the strap it is replacing, and because it tends to flex and move inside the starter, meaning that it could possibly get in the way of the armature or come to rest against the field case or a pole shoe and chafe through to create a short.

_________________

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 11:03 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:32 pm 
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Field Case, continued


Once the straps are all found to be serviceable, any shorts in the coils themselves should be repaired. This is the most difficult repair to make in the field coils. Fortunately, it is the least common. First, the short has to be located. This most often requires carefully removing the insulating paper from suspect areas (do not remove any more than you have to. There is no better insulation for the field coils than this paper, as it is designed specifically to do this job and in this environment!). If the short is on an outer winding, it is easiest to simply clean it as best possible and bridge the shorted area with solder. When the solder cools, lightly work it with a file to shape and flatten it, then rewrap the coils. If the short is on an inner-most winding (against a pole shoe), then the same principal applies.

If the short is inside the windings of the coil, the easiest advice is to discard the coils. However, as replacements cannot be found, there is nothing to lose by attempting to open the coil and effect a repair. Remove all the paper from this coil-- carefully, as you do not want to cut through the insulating varnish where it is still intact. The coils are pulled tight by a machine and the varnish acts as a glue to help keep them tight as well as prevent "shortcuts" by the electricity that might (but also might not) weaken the strength of the magnetic field. Do not attempt to completely unroll the coil and lay it out flat; it will be impossible to reform them tightly enough to both fit and function. Instead, try to tease them apart, loosening them only enough to find and repair the short.

Reparing a short inside the field coils is difficult at its best, infuriating in general, and impossible at its worst. The only way to really repair such a short is similar to bridging bars on the commutator. When the short is found, clean both top and bottom surfaces of both ends of the short. Then clean the touching surfaces of the two adjacent windings. Solder the both ends of the shorted winding to the winding under it, and then solder the winding above the shorted leads to the shorted leads. In effect, you will have three windings soldered together. This is necessary, as the windings must lay as flat and as tight as possible in order to fit tightly together as a coil. It would not be possible to file off a blob of solder from the shorted lead, as the repair would separate. After the repair is made and continuity is restored, file the repair as flat and thin as possible, paying particular attention to any run off solder at the edges of the coil. Lightly spray the soldered windings with insulating varnish or epoxy-based paint. Do not try to use liquid tape or electrical tape inside the windings of the coil. Wind the coils as absolutely tightly as possible, tying them off with string if need be. Spray the entire coil lightly with insulating varnish (or your epoxy paint). Re-wrap the coils. Odds are that the coil paper had to be cut off, so alternative insulation will need to be found.

_________________

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 11:05 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:36 pm 
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Field Case, continued



Once the field coils show continuity from the positive stud through to the positive brush lead, it is time to fix any shorts to ground. Shorts to ground come from one primary source: insulation failure. Examine any uninsulated sections of the field coils, looking for signs of shorting. As uninsulated sections are not expected to ever come into contact with the field case, this can indicate that a section of the field coils (usually the straps) was bent, most likely during a prior repair attempt. Often, the joints of the bridging straps are left uninsulated. They can be easily insulated with liquid electrical tape. Sometimes the coil paper is torn or has been burned through from heat rather than a short. If the tear is tiny, a small application of liquid tape, left to dry, will often solve the problem. If it is more than a nick, however, you will most likely have to rewrap at least that leg of that coil. Find all the areas that will need to be rewrapped. Spray them with insulating varnish (as always, spray alight coating. It is not intended to be a paint). This will help to insulate the coils if you are forced to use a substitute insulation and it will help to hold coil paper in place. Unless the coil paper is ragged or unraveling, it should not have to be removed. One, or rarely two, additional layers of insulation will solve the problem in most cases. If the original paper had to be removed, use two layers to re-insulate. Do not use any more additional insulation that needed, as distance is an insulator against magnetism, and the coils should be as close as possible to the pole shoes. Also, clearance between the coils and the armature is very tight; if the insulation rubs the armature the least bit, the armature will remove it in short order.

Field coil insulating paper may be obtained from various specialty vendors, but for most people it will be difficult or impossible to locate. Fortunately, there are other (lesser) choices. Three-quarter inch masking tape, carefully wrapped in no more than two layers may well do the job. Be careful if you opt to use the masking tape: you will need to allow small (very small) excess amounts on the inside portion of the coils (the part that rests against the pole shoes) so that it will not tear against the pole shoes during reassembly. As a last resort, electrician's tape may be used to insulate the coils, but it is the poorest choice, owing to its thickness (use only a single layer) and the tendency for heat and moisture to both soften its adhesive and deform its shape. It also tears easily against the pole shoes, and its thickness prohibits leaving and slack in it to prevent this. Additionally, the final coat of insulating varnish cannot be applied to it, as it will not dry on the vinyl of the tape. Whatever you use, make sure that the coils are completely covered, as even areas that do not lie directly against the field case can be shorted by the eventual collection of brush dust.

The field coils may not have had any shorts to ground. If not, there is no need to re-wrap them unless removing them damaged the coil paper. However, it is not uncommon to find bits of rust from the field case stuck to the coil paper. Do not tear it from the paper! This will usually just tear away at the paper, requiring the coils to be rewrapped. If there were no shorts, then the rust has not done any damage. Lightly brush off what can be readily removed, of course, as the less debris there is, the easier the coils will be to reinstall. When the coils have been made ready to reinstall, give them a last light but thorough coating of insulating varnish and let it dry completely. This is not just insurance against possible shorts to ground, it will also make reassembly a little easier, as the insulation will be that much harder to tear. If you have been forced to use electrician's tape, do not spray this final coat on the electrician's tape; it will not dry, and will simply gather dust and debris in the starter.

While the field coils are drying, inspect the field case. At this point, it is just a steel cylinder, smaller than a beverage can, with five small holes in it. Look inside the case. Any rust or corrosion should be completely removed. Sandblasting is ideal (be careful of the locator marks you have made for the pole shoes! At this point, it is wise to transfer your marks to the outside of the case), but use whatever methods are at your disposal. Clean the inside completely. This is also the best chance you will ever get to paint the field case, if you are planning on custom colors for your engine. If your field case has any dings or hammer tracks from having been tapped, dropped, or beaten, you can sand them out (or fill them, as the case may be) while you are waiting for the field coils to dry. It goes without saying that if you have to fill them (personal choice; I seldom do myself), you will probably end up painting the case to make it look right. (which is why I seldom fill them).

Once the inside is completely clean, coat it with a smooth, thorough layer of insulating varnish. Two coats is ideal. If actual insulating varnish is used, take a break; it will be some time before it is dry enough to handle again. Do not try to speed the drying process with heat or light; this will simply cure a "skin" onto the varnish, and will actually impede drying time greatly.

_________________

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 11:07 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:46 pm 
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A Few Details


This is also a great time to look at the windings of the armature. If the stacks (the laminated metal bars around which the windings are laid) have any rust or flakes on them, gently sand it off. Spray a light coat of insulating varnish on the stacks to impede further rusting. Do not give in to the temptation to completely paint it; a light mist coat is sufficient.

Take a moment to get the commutator end frame. Mask off the inside of the top, where the bushing and the holes for the brush rack mounting screws are. When you are done, only the inside of the walls of the frame should be exposed. Apply a good coat of insulating varnish to the inner wall of the frame. This is not necessary, and is never done during the factory assembly process, but it does provide a good bit of protection against an errant positive brush lead shorting against the frame. Remove the tape and allow the varnish to set while you are waiting for the field case.

Once the inside of the field case is dry, remark your notations for the pole shoes. If the outside of the starter is to be painted, take note of your ditto marks. Be sure that they are not obscured or filled by the paint. If you used a marker instead of actual ditto marks-- well, you might want to skip painting until it's all back together. If the outside is to be painted with a metallic paint, take precautions to ensure that no overspray gets inside the case.

No matter what type of paint you use, take care not to paint the surfaces of the commutator end frame that will rest against the engine, or the surfaces of the drive end frame that will rest against the engine. These surfaces serve as the ground for the starter; paint will impede the ground, and therefore the function of the starter.

As soon as the case can be handled, begin to reassemble the starter.

_________________

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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PostPosted: Tue Jul 03, 2007 9:49 pm 
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Reassembly


Gently work the field coils into position, poking the positive stud through the case last. Take care not to scratch through the layer of insulating varnish (it will likely be several more hours before it is completely cured), but as soon as the unit can be handled, the starter can be used; the varnish need not be completely cured.



Using the marks as a selection and orientation guide, carefully place the first pole shoe inside the field coil. Manipulate it until the threaded hole lines up with the hole in the field case and start a pole shoe screw into it to hold it in place. Do not run this screw up yet. Simply wind in two or three threads to keep the shoe in place; the field coils will have to be manipulated for each shoe, and leaving some wiggle room for the shoes will make this much easier. Once all the pole shoes are in place, run them up tightly with a #3 Phillips screwdriver. Secure them further with the impact screwdriver, but be careful not to deform the field case or strip the screws. When they are tight, inspect the inside of the case. Ensure that the coils nor the shoes can be moved, and ensure that they shoes are pressed tightly against the field case. If there is room to run them up even the least bit, do so. They must not touch the armature.

There is a definite trick to tightening pole shoes. After all, if you use an impact screwdriver, you are effectively striking a hollow cylinder with a hammer. We all know what happens to hollow cylinders that get struck with hammers, and we all know the importance of the armature's precision placement between the pole shoes.

These two bits of knowledge are rather at odds with each other, aren't they?

There is a device called a "pole shoe machine" (and various other, less-printable names) that any rebuilder worth the name will have handy. However, most back yard mechanics will not have this handy. Because of this, a work-around has been included:

Ideally, this is done with a pair of bench vises. Since few people have two bench vises, and since this isn't really "approved technique," there's really no reason not to try it with just one bench vise...

Get a length of sturdy pipe or a section of wooden post that will just fit through the field case. Fit it into the vise such that it protrudes horizontally from the jaws. Slide the field case into place over the pipe. This will isolate the hammering to just the supported area, and not distribute the blow across the entire cylinder, which greatly increases the odds of deforming it.

Another note:

sometimes, the impact driver isn't enough, and the pole shoe screws may have to be drifted in. If you don't know what this is or how it's done, then take it to someone with a pole shoe machine or _lots_ of practice with the drifting technique. Also accept that most screws, once they've been drifted in, are now permanent fixtures of whatever they've been drifted into.

Back on the outside of the field case, center the positive stud in its hole, and reinstall the O-rings that insulate it from the case. Install the insulators and nuts in the reverse order of removal. If any insulators have been damaged, they will have to be replaced. Radio Shack and automotive electrical repair shops may have suitable replacements. Odds are that the exact insulators will not be available, but common sense will indicate what will or will not work. There should be enough depth to the insulator and nut combination that there is no chance for the starter wire to touch the body of the starter.

Once the positive stud is secure, look inside at the bridging straps between the field coils (remember, they are on both ends of the case) and ensure that they are not touching the field case. They can come extremely close, but if they are touching, use a suitable tool to gently pry them away from the case.

Take a few minutes to run some continuity tests. You should NOT have continuity from the starter positive bolt to any other point on the starter at this point. If you do, find out why. You may have to disassemble the field case again, but it's better to do so now than after you've fully assembled it. Once you are satisfied that there are no shorts, continue on.

Reinstall the armature from the drive frame end, commutator first. Gently work it through the field coils and inspect the coils for any damage to the insulation and to confirm that none of the straps have been pushed into contact with the side of the case.

_________________

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 11:17 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:56 pm 
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Reassembly, continued


After the armature is installed, install the paper gasket to the commutator end of the field case.
Now get the brush rack. Orient it to the position in which you removed it. Some, but not all---- even among units of identical model number-- field cases may have something such as a pin or dimple to indicate the orientation of the brush rack, but if not, there is a way to figure out the correct orientation:

Find the ditto marks on the field case. Align the commutator end frame with the ditto mark. Carefully remove the end frame, noting its exact orientation. Inside the commutator end frame is one or two ribs. These ribs orient the rack. The rack must be installed so that it will fit into the commutator end frame when the ditto marks of the field case and the frame are aligned. This method is a bit awkward, but in a large number of cases, it is the only option available should you fail to remember the correct orientation.

As this is a two-brush starter, there is little need to "set" the springs. Setting the springs is a process in which the brush-contacting ends are pulled back through the brush brackets and pulled slightly so as to force them to come to rest against the top edge of the bracket or against the side of the brush itself. This allows the brush to be pushed back into the bracket enough to make installation of the rack around the commutator a simple procedure. As soon as the rack is aligned and the positive brush lead is installed, the brushes are pushed forward and the springs are released. If you opt to set the brushes, be very careful, as the springs are extremely easy to dislodge and lose.

As an alternative to setting the brushes, I try to keep a selection of old deep-well sockets, bits of pipe, wooden dowel, and other things of varying diameter just lying about. Find a cylinder of nearly the exact (or better-- slightly larger!) diameter as the commutator, and slip it through the center of the brush rack. Set the brushes by simply working them back into the rack to make room for your spacer. Work the rack onto the spacer.

This way, you simply place the rack over the commutator, and slide it down the cylinder onto the com; the brushes will be in place.

Secure the positive brush to the positive brush lead with the #2 Phillips screw (clean it if it is rusty; this is an important connection). If it is available, apply a small amount of dielectric grease to all the mating surfaces involved in this connection. This will improve the connection and safeguard against premature failure of the connection. It will also seal out oxygen, helping to prevent future corrosion. Release the brushes if you have decided to set them.

One word of caution: for some reason, the first time people attempt to rebuild a starter, ninety percent of them will attempt to install the brush rack upside down. I don't know why this is, except perhaps it "looks more right" to someone who has never done it before. The brush rack should be installed such that the flat plate of the rack seats up into the commutator end frame and the brush brackets face down toward the field case. They do not fit inside the field case (a mistake that accounts for half the people who install it oriented correctly), but fit roughly centered on the commutator.

_________________

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 11:22 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 9:59 pm 
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Reassembly, continued

Find the two holes in the brush rack that the brush rack mounting screws will fasten into. On many racks, they will be on sections of the that are raised slightly from the rest of the rack (this is to help guard against accidental grounding of the positive brush). As Mitsuba does not manufacture this part (and it is available from the aftermarket!) but instead buys them from the lowest current bidder, there will be some variation from rack to rack. But they will all have two holes for the brush rack mounting screws. Apply a very small amount of dielectric grease on the area immediately around these holes. As with the positive brush lead, this is to help slow corrosion at this connection and to help ensure a consistent ground. A tip for easier installation: after finishing the brush rack installation, tug it "upward" toward the end of the commutator as much as is possible without slipping the brushes off the commutator. This will ensure that the rack is close enough to the commutator frame that the mounting screws can easily reach it. It can save you from having to remove the frame numerous times to position the rack.

If you managed to salvage the rubber O-ring gasket that seals the commutator end frame and the field case, install it on the field case now. It fits over the stepped ridge on the outside of the case. If you do not have that gasket, one can be obtained from the aftermarket, but only as part of a seventy-odd dollar parts kit. If you do not wish to buy that kit (and it consists a brush rack, brushes, the two bushings, and the O-ring seals), a perfectly viable solution is to paint a very small bead of liquid electrical tape around the edge of the field case. As the commutator frame slides over the case, the tape will seal against it. Do not use silicone or RTV, as these are not actually adhesive, and require a great deal of pressure and surface area to properly seal. It will peel away from the surfaces as it ages. Wipe off any excess liquid tape after the frame is in position.

Before installing the commutator frame, make sure that the bushing is free of grit and debris and be sure to put a small amount of cam lube or lithium grease inside the bushing-- just a small amount. The bushing is oil-impregnated and will not require any lubrication within its lifetime. This first bit of lube is simply to help the frame slide more readily onto the shaft and to assist in "burning in" the bushing to the shaft. When you install the frame, take care that the brush rack is aligned with the guides inside the frame, and be sure that the frame mounts completely down onto the field case. The frame can be tapped lightly with a non-marring hammer or drift to assist in seating it. If you do not have the original O-ring installed, expect to leave a slight (less than one-sixteenth of an inch) gap between the frame and the O-ring lip on the field case. Double check to ensure that your ditto marks are aligned correctly. Get the brush rack mounting screws and the o-ring seals that fit around them (if your starter had them) and secure the brush rack to the commutator end frame. The rack may have to be manipulated slightly through the holes in the frame. Use a pick tool to align the mounting holes, then securely fasten the rack to the frame. Be careful not to push the rack down into the frame. If the rack is too low inside the starter for the screws to reach it, the frame will have to be removed and the installation process repeated. (This can prove quite messy if liquid tape is used in place of the O-ring.)

Set the field case aside for now and set the drive end frame back into the vise, secured lightly against the bottle neck as it was when you disassembled the starter. Locate your ditto mark on the frame and make sure that it is turned so that you can easily find it. If you have not done so already (and you should have), lubricate the stationary gear, planetary gear posts, and planetary gears with high-temperature high-pressure grease. The frame need not be filled with grease; there should be enough that after the gears are run briefly, all the meshing faces will be coated.

_________________

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 11:26 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 10:01 pm 
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Reassembly, continued


Place the O-ring seal on the field case as with the commutator end. If the seal is not available, the substitute liquid electrical tape as above. Carefully, so as not to dislodge the armature, stand the field case up and insert the splined end of the armature in the space between the planetary gears. Slide the field case into the drive end frame. Verify that the ditto marks are correct.

Reinstall the through bolts through the tabs in the commutator frame and into the drive frame. Tighten the bolts securely, alternating periodically to ensure that the assemble goes together straight and without binding.

Once the starter is re-assembled, it must be tested. As before, secure the starter-- most easily done in the vise. Attach a ground lead from the case of the starter to a 12v battery (most battery chargers will not put out sufficient amperage to properly test the starter, though they may spin it). Secure a positive lead to the positive stud and touch it to the battery. The starter should spin easily and powerfully, leaping to very high RPMs. If not, try lightly tapping the frames against the long axis of the starter; it is possible that the new bushings are not aligned correctly. If there is no change with very few blows, the starter will have to be disassembled and re-inspected for problems.

If there is any arcing when power is applied, ensure that the starter body has a good ground and check to make sure that the positive wire is not touching the starter body. If the problem is not external, re-open the starter and examine it for possible causes, such as brush leads touching ground or damage to the field coil insulation. Generally, if you can read continuity from the positive stud to either end frame or a pole shoe mounting screw, there is an internal short.

If these directions were carefully followed, there should be no complications. They are based on several years of practical experience, dozens of teardowns and repairs on Mitsuba 2-28 starters, and the complete teardown and rebuilding of two Mitsuba 2-28 starters specifically for the Honda Rebel CMX250.

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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_."


Last edited by Duke on Mon Jun 21, 2010 11:27 pm, edited 1 time in total.

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PostPosted: Tue Jul 03, 2007 10:04 pm 
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Leftovers:

[These are two pieces that were moved during the editing process, but never 'installed' back into the text. They would have been early in the disassembly section, and contain important data.

If the mood strikes me, I may work them in. For now though, I'm going to bed:

Edit/move:

While the penetrating oil is soaking on the through bolts, locate the two screws that run into the commutator frame. Apply penetrating oil to those screws as well


While the oil does its job, locate the positive post. This is the threaded stud that protrudes from the field case. The power wire from the bike was attached at this point. Notice that it has one (or sometimes two) nuts still fastened, and a varying number of thin, round, washer-like insulators. Remove the nuts (in most cases, they will be ten millimeters) and carefully remove the insulators. You may find it expedient to work the insulators loose with a pick tool as you go along. Pay close attention to where each insulator was located in relation to the field case, the other insulators, and the nuts. If you have to, get a marker or other device and label them

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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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PostPosted: Tue Jul 03, 2007 10:07 pm 
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And that's it.

That is the single most comprehensive thing I think you're likely to find on the starter for the Rebel 250. Yes, most of the information there can apply to any bike starter, and a great deal of it will apply to any starter, period.

Please keep in mind that there are a few more 'leftovers' scattered around my hard drive. I'll try to post them up here as I find them. In the meantime, feel free to ask questions or clarifications.

For the record:

I tore down two starters, but the same model. One had pole shoes (the one from Jack) and one did not. IF yours doesn't, then you've got it made:

you'll have rare earth magnets, and the only thing you'll need to do with your field case is clean it and make sure the magnets aren't broken or cracked. there are no pole shoes or coils in a permanent magnet starter. Luck you!

I will be glad to discuss anything in these posts, but not tonight. It took a couple of hours just to move all that stuff over here, and I'm going to bed.

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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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PostPosted: Wed Jul 04, 2007 6:52 pm 
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almostfamous:

is any of this any good to you?

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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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PostPosted: Sat Jul 07, 2007 4:36 pm 
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Well, either I did well--

217 views and no questions--

or I did poorly and it has no value for 217 people...

:lol:

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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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PostPosted: Sat Jul 07, 2007 6:06 pm 
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That is the most exaustive HOW TO i've ever seen ... EVER.

Thanks Duke, I've printed this off and filed it with my Rebel Repair Manual (a guide i've started with posts from here). I'm sure this will come in handy one day.


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PostPosted: Sat Jul 07, 2007 6:15 pm 
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Thanks.

Like I said:

Duke wrote:
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.



And

Duke wrote:
I decided to go ahead and write up a comprehensive guide to rebuilding the specific starter used for the Honda CMX 250.


You didn't think I lie to you, did you?

Remember, it was intended to be a book originally. Without pictures, it's over thirty pages long. There were nearly eighty diagrams I couldn't post (file corrupted), and of course I never did have the opportunity to get pictures added.

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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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PostPosted: Mon Jul 09, 2007 5:19 pm 
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Almost forgot:

Bobby:

If you'd like, you've got permission to mirror this on your site, so long as the "blurb" remains intact.

Same for your board, Jason.

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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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PostPosted: Fri Jul 04, 2008 11:55 pm 
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As luck would have it,

I have been having starter issues of late with the Valkyrie. Given its mileage and its status as a daily driver, the natural assumption was 'brushes.' So I ordered the brushes and a loaded brush rack from Bike Bandit, which shipped five days after I ordered it, meaning just in time to not move because of the holiday weekend, so maybe I get them in time to make my trip next weekend; maybe I don't. I hope so, but hey--

at any rate, I pulled the starter off today so that I could go ahead and prep the starter, inspect it for other wear, and of course, paint the field case. Yes; that's important. The field case, out of necessity, is made of steel. It will rust eventually, and mine has shown a faint hint of orange here and there-- just a tint, really, but it never gets better ;).

I remembered posting this some time back, and decided that I'd try to get a few photos so that you could see what's what.

I didn't edit them into the guide simply because it's the wrong starter. Yes, most people wouldn't notice, but some might get worried if they opened up their starter and it didn't look identical. It doesn't really matter, as the techniques are all the same.

But anyway, I got some shots. I didn't get all the shots of every procedure (because it just doesn't seem necessary to explain things like "soak with degreaser), but that's largely because I am not going as deeply into my starter as a complete rebuild.

First off, for those of you who have never had to remove a starter from a Valkyrie, be very, very happy.

The only thing left on that bike right now are the fenders and the engine. Man what a bear that was.

Secondly:
turns out my problem was not the starter.
It also turns out that it is _now_... :lol:
Seriously, though-- upon inspection, I still had about 1/3 of the useful life of the brushes, so I had to look elsewhere for the problem. Found a really interesting design flaw in the wiring, and found it mirrored on the Rebel! More on that later.

I'm way past bedtime, and working on a sudden shot of adrenaline.



This picture shows the removed starter. Notice the three sections. From the tail, they are the commutator end frame, the field case, and the drive end frame.

This picture also shows the positive terminal, which carries the electricity to the brushes.



A close-up of the commutator end frame, showing the stamping of the make and model number of the starter. Like the Rebel (and most other import motorcycles), it uses a Mitsuba starter.

Also visible is the head-end of one of the through bolts.



A closer shot of the positive terminal.
You can see that there is an insulator between the field case and the nuts. This prevents the terminal from shorting out on the case itself. There are additional insulators inside the case, and one that passes through the case itself. The bottom nut holds the insulators in place and keeps the terminal from moving. Your positive wire will actually fasten between the nuts.

Note the rubber gasket at the end of the field case. There is one at each end. Don't damage them if you can at all help it.




I mention "ditto" marks in the write-up. This is because with many starters, the field case will only fit one certain way. You can use anything you want-- sharpie, if you like. I used a light spring punch because the marks are small, unobtrusive, and permanent. I will never have to mark this starter again, no matter how many times I tear into it.

Be careful if you're using a hammer and punch! You can easily damage the cast aluminum of the end frames, or even deform the field case. Either one will likely as not ruin the component.



Notice that the ditto marks are different one end to the other. One the drive end, they are paired, and on the comm end, they are single.

This is a habit of mine, and it exists for a reason. Many starters-- marine in particular-- can have their rotational direction reversed simply be inverting the field case. I don't want to do that ;). Another thing is that there are also many starters that the field case can only fit one way, even though it _looks_ like it can fit either way. If the marks specifically designate orientation, I can avoid a few minutes of aggravation. ;)



Disassembly begins. Break loose all the through bolts before actually removing any of them. This helps prevent bending a through bolt or deforming the end frames.


And that's as far as I've gotten today. I've also fallen asleep twice composing this post.

I'm going to catch couple of hours before I have to go to work ;)

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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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PostPosted: Sat Jul 05, 2008 11:34 pm 
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And now the rest of the pictures-- at least the ones that came out.

As stated before, I didn't go as deeply into this starter (there was no need), so you won't see many of the components discussed in the write up, but I figured this might help some folks.

Further, not all the pictures I took came out-- only fourteen of them were worth using.

But here we go:

When you remove the commutator end frame, you'll see something like this:



Note right off that the armature slipped some in the field case, and the brush rack has been pushed away from the field case. Thus, the brushes are not on the commutator, but on the commutator end armature bearing.

Clearly visible are the opposing positive and negative brushes and their leads. The negative leads are bare, and spot welded to the rack, as they will ground through the case to the engine. The positive leads are insulated to prevent shorting to the case or the rack, and the brackets holding the positive brushes are mounted on laminated insulating plates made of the same material as the insulators on the positive post.

The coiled springs push the rear of the brush, ensuring constant contact to the armature.



Nothing special here; just another view of the brush rack. Nice close-up of the spring, and of the insulation on a positive brush lead, but it's so smutzed up it doesn't show well.



The brush rack removed.

The insulators that are marked are those insulators from the positive post. They are stacked under the nuts to raise the wire terminal away from the field case, eliminating the chance of an arc to the field case.

Also visible is the antique spring punch I prefer for ditto marks ;). You can see how the springs (which are surprisingly strong) push the brushes out of the rack, and you can see that I totally forgot my own shortcut-- putting a socket inside the brushes before pulling the rack, as getting all the brushes back in place at once (without drilling for brush pins, anyway) is really awkward.

Actually, I didn't forget. I dropped the rack (greasy fingers) and the socket popped out of place. Disappointing, but hey-- these things happen.

Note the black ring on the positive battery post. More on that in the next picture.



I'm not much of a photographer, but you can see the rubber ring around the positive post. This actually centers the post to keep it from touching the field case where it passes through it. It fills the hole around the post and insulates from the case.

The larger plastic piece is an insulator also; it keeps the strap from touching the field case on the inside of the starter.

The strap is difficult to see, but it is the piece that carries current to the positive brushes. The leads for the positive brushes are welded to the ends of the strap. When installing the new hot brushes, make sure that the insulated sleeve is tucked down into the field case, lest it arc and short your starter.

The red thing has nothing to do with the starter. I'm not sure what it is, or where it came from. But it pleases me, so I haven't moved it off the bench.





First look inside the field case. This is the drive end of the field case, and the armature is still inside it. Clearly visible is the drive spline of the armature shaft, the drive end bearing, and the copper of the armature windings.

None of the pictures with the center plate still in place came out. I have no idea why. But once you remove the center plate, the view in the above picture is what you will see.




The armature, all naked and alone. I had no need to pull the bearings, so I didn't.

Also visible is one of the field case gaskets, a through bolt, and some assorted bits of other projects ;). If nothing else, the saw blade and twelve-foot tape measure should give you an idea of scale. The coat hanger provides a translucent softening of an otherwise overly-macho work bench. ;)

Note the black strip around the commutator. This is carbon scarring. Well, it's just staining at this point, as the commutator, for all the use this starter has seen, is astoundingly unworn. I didn't even need to lathe the commutator; it cleaned up sufficiently with a green scotch pad, and had not so much as a single pit or divot anywhere. I was very happy with the condition of this armature.

The "stacks" are laminated steel plates with notches cut in them. The windings pass though the notches. They provide the steel mass used to harness the electromagnetic field generated when the brushes are energized.


Of all the pictures I took of the empty field case, I'm afraid that this is the best one:



The only distinguishable feature (digital cameras have their drawbacks-- the auto-focus / macros / flash combo is evidently one of them ;) ) in this picture is the hole through which the positive terminal passes.

Not easily discernible is the insulated trough that houses the positive brush strap, the notches that secure the brush rack into position, and the rare earth magnets.

I really wish the magnets had shown, if only to illustrate just how fragile they are. It might get more folks to STOP SMACKING THE STARTER when it fails to work properly. You crack one of these hyper-brittle babies, you're looking for a new starter. In the case of the one you're looking at, it's over six hundred bucks. (See? There's a reason to learn all this, isn't there? ;) )




I'm afraid that this is the last useful picture I took.

It's the inside of the drive end frame. Visible are the two planetary gears and the ring gear in which they orbit. The armature drive spline centers between the planetary gears and turns them against the ring gear.

The plate that the gears are mounted on is thus turned, which spins the output drive spline visible on the assembled starter. That shaft is nothing more than an extension of the center of the plate.

The planetary gears are mounted on posts, also cast into the plate. They ride on internal bushings or needle bearings (in this case, bearings).

The astute person with a grasp of gear physics will immediately notice that the drive end assembly is nothing more than a simple series of levers and counter-levers designed to trade the speed of the armature for actual torque. The final output shaft spins much slower than the armature does, but it's also _much_ harder to stop ;)


I did not take any picture of re-assembly. I had to get done, and frankly, stopping to totally clean my hands every few second so I could handle the camera turned a three-minute tear-down into a two hour project, and I just didn't have the time to take snaps of the put-back. Further, I was bereft of volunteer photographers. In fact, the only one handy simply asked "who in their right mind would stand there taking pictures of the guts of a machine? Who would want to look at something like that?"

Ah, marriage...

I will try to snap one picture of the thing back together, if only to prove that it can be done ;).

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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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PostPosted: Tue Jul 08, 2008 7:44 pm 
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And the finished product.

I don't have my sandblaster cage set up, so I didn't bother doing much with the aluminum drive frames save just cleaning them up with degreaser and a scotchbrite pad,

but this is the completed stater:




As you can see, since I didn't have my bench vise available (it's currently holding a project for a buddy of mine), I just bored a hole in the work bench to stand the starter in. Worked like a charm ;)



And no; that's not the original color of the field case. There's just so much of that Honda aluminum-colored paint under the tank already. Besides, every starter I've ever rebuilt I've painted "cast." I just like the way it looks ;)

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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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PostPosted: Thu Jul 31, 2008 11:29 pm 
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Been tinkering with another starter, and figured hey-- why not get some more pictures.

This is an entirely different starter as well-- it's off an 80-something four wheeler.

But it seemed reasonable to write up and post for a couple of reasons: it shows some of the differences in starters, and the similarities. Mostly, it shows that everything I've written above will let you rebuild pert' near _any_ motorcycle starter. (if someone wants to send me a five-sided solenoid Nippon Denso, I'll do one of those, too ;)

First thing to note is the construction:

Like _all_ starters, there's a three-piece case: Commutator End Frame, Field Case, and Drive End Frame.

In this case, note that the drive end frame is much shorter than that of the Valkyrie / Goldwing starter in the pictures above. This is a tip-off about what you're going to find. There's no room in there for a gear-reduction set-up, so you know right off we're working with a 'direct drive' starter.




and it is, as is normal with a bike, yet another Mitsuba:




And, if you've got really good eyes, you can even see right off the bat what's wrong with this thing, and that it's not worth rebuilding:



unfortunately, the pictures of the armature that help to demonstrate the issue didn't come out (seems any time you turn my camera off, it automatically turns off the macros.)

Anyway, this starter has been swamped. That is, the machine has been submerged for more than just a second or two. It's pretty obvious, when the output shaft, which receives engine oil, is rusted to flaking. Further, it's actually rusted to the bearing that it rides in!

I called the owner at this point and asked if he was sure he wanted to save it. He informed me that it had never been swamped, and he wanted it fixed. I told him that it had. "Duke, I bought it new and ain't nobody but me ever rode it." Yes; they have. The sank it in a sippi hole somewhere.

After some investigation, it turns out his son swamped it about a year and a half ago, towed it home, and changed the oil so Daddy wouldn't find out. He didn't know enough to open the starter and dry it out and re-lube everything.

At any rate---

Pulling it down is just like any other starter: make your ditto marks, pull the through bolts (which are internal on this unit), and start disassembly.

Shame the shots of the armature weren't worth keeping. The amount of pitting and rust scale on the shaft was legendary!

So I called the owner again, to ask if he was _absolutely_ sure, because this was going to get really expensive, really fast. (time-wise, anyway).

Seems that this four-hundred dollar starter was discontinued about ten years ago, so yeah; he was sure.

It should take less than an hour to completely rebuild this starter.

I spent four hours on the armature alone.

The damage was total. The short version:

The starter was swamped, for several hours. It took on water, which was never dried out of the starter. The water got into the drive end bearing and displaced the grease, which ruined the bearing. It also started the pitting process on the armature, which accellerated the destruction of the bearing. As the armature began dragging, it took more and more amperage to turn the starter, which increased wear on the brushes and the commutator. The increased heat of the upped amperage and dragging armature burned the commutator pretty badly. A portion of the brush rack itself had rotted away from rusting.



More to come. IT's really, really late.

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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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