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 Post subject: CMX250 Sprocket Conversion
PostPosted: Fri Apr 06, 2018 7:07 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
Hello dear rebel riders,

I am looking for some information. Has anyone had any experience with 520 sprocket conversion to 428 on rebels? Would placing a CG/CB 428 sprocket cause any kind of drive issues?

As attachments are not working. Kindly check JTF259 and JTF270 for reference.

regards,
Arshad


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Fri Apr 06, 2018 5:04 pm 
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Joined: Feb 23, 2009
Motorcycle: Rebel 250 plus a few others
Rebel: 250
Country: Canada
State/Province: NB
City: Fredericton
I'd advise against it. Heavier (longer pitch) chain is indicated when the horsepower to be transmitted goes up. Rebels are low horsepower machines that are quite happy with 520 chain.
Why not go with stronger longer pitch chain?
First its not needed . 520 will last a very long time if maintained properly.
Second, and most important. Longer pitch chain requires bigger pitch diameters on the sprockets for the same tooth count. The countershaft sprocket space is extremely limited, so a 428 sprocket would need to have fewer than the stock 14 teeth of the stocker to fit in the same available space. The fewer number of teeth, the more chain speed variation and mechanical stress will occur due to the fact that the sprocket is not a true circle but a polygon with the number of teeth minus one sides.
Thus there is no reason to change from the stock chain pitch and a good reason not to.

_________________
2004 Honda Rebel 250
2003 BMW K1200GT
2004 BMW R1200GS
1996 Ducati 900SS
1973 Norton 850 Interstate
1968 Triumph Bonneville


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sat Apr 07, 2018 8:29 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
Thanks for the feedback but i think you may be confused with 530-535, 428 pitch is shorter and the sprocket 520 count of 14 = to 428 17t count in size. But i do agree that the rebel being a low power engine goes smoothly with 520, would you agree that a 428 would naturally allow for a little more power due the weight decrease relieving some stress on the engine.

My concern mainly was about the design of the sprocket itself, if you analyze the designs both of them have exact same dimensions except for the pitch and the rebel having a circular inner thickness of an addition 0.5 where the mounting points are. I was only concerned about that causing riding issues while not being present on the CG sprocket. But same as many bikes changing 520 to 428 to gain some overall power i do not think pitch change should be a problem.

still any more feedback is much appreciated. thanks


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sat Apr 07, 2018 2:54 pm 
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Joined: Feb 23, 2009
Motorcycle: Rebel 250 plus a few others
Rebel: 250
Country: Canada
State/Province: NB
City: Fredericton
Ouch... Yes of course you are correct. 428 chain is a half inch pitch vs 5/8 inch pitch for 520. However, I still don't recommend making a change from the stock size.
IMO the extra power transmitted by a smaller chain (if any) would be undetectable by a rider . The smaller sprocket teeth and roller pins would also tend to wear faster in the rather hostile environment of a motorcycle chain since they are smaller to begin with and a slight erosion of a smaller tooth would be more significant than the same wear on a larger tooth.
All in all, IMO there is little to be gained by trying to re-engineer what Honda has already done reasonably well. As an owner your time is much better spent maintaining your equipment in excellent condition.

_________________
2004 Honda Rebel 250
2003 BMW K1200GT
2004 BMW R1200GS
1996 Ducati 900SS
1973 Norton 850 Interstate
1968 Triumph Bonneville


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sat Apr 07, 2018 3:17 pm 
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Joined: Oct 16, 2005
Motorcycle: 2014 CB500XA
Rebel: None
Country: USA
State/Province: AZ
City: Green Valley
I think that a few racers shifted to 428 chain and sprockets running old-fashioned chain (no o-rings or x-rings) for reduced frictional losses.

_________________
John, 2014 CB500XA (Daily Rider), 2009 CRF230L (L'il Red Piglet), 1989 NX250 - sold, 2001 Rebel - sold; first bike was a gently used 1958 Matchless G2 (250 thumper)
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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sun Apr 08, 2018 3:18 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
Yes Jsonder, that is the kind of info i am looking for exactly. I thought of running some 428H on it for the extra power. thanks for the feedback


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sun Apr 08, 2018 6:32 am 
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Joined: Feb 23, 2009
Motorcycle: Rebel 250 plus a few others
Rebel: 250
Country: Canada
State/Province: NB
City: Fredericton
http://www.didchain.com/standardChains.html
Interesting that DID (one of the most reputable manufacturers) specifically advise against using standard (non O ring) 428HD chain on anything bigger than a 125.
The extra half horsepower you might get out of the most efficient chain drive needs to be weighed against the decreased chain and sprocket life to be expected. Will you even notice an extra fraction of a horsepower, and is it worth the reduced chain life/increased chain maintenance requirement?
Like everything else, modifications are a tradeoff. There are advantages and disadvantages.

_________________
2004 Honda Rebel 250
2003 BMW K1200GT
2004 BMW R1200GS
1996 Ducati 900SS
1973 Norton 850 Interstate
1968 Triumph Bonneville


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sun Apr 08, 2018 7:52 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
no that is a myth duckster, you cannot deny what has been in use for like a few hundred years. Remember when big bikes knew standard chains and not o-ring. You cannot just simply say non o-ring is death kind of nay saying. Racers still use non-oring up to 300cc to trade power for longevity. sprocket and chain change half of a 520 mileage is ok for me for some performance gain and from what i see you completely misinterpreted what D.I.D is saying.


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sun Apr 08, 2018 11:01 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
Still it is true that it is most recommended to not downgrade to non 0-ring on bikes that come with o-ring, but the reason for it is that they are high power bikes that do not suffer from o-ring and at the same time need the o-ring setup to hold under pressure and last properly for that engine. There are many cases where i am that i myself have used non o-ring on bikes that came with 0-ring absolutely no issues except for the more frequent lubrication requirement, mileage is a fraction less but all ok.

if any1 has any more feedback it is most welcome, i really enjoy the discussion on the topic so far.


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Sun Apr 08, 2018 3:17 pm 
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Joined: Feb 23, 2009
Motorcycle: Rebel 250 plus a few others
Rebel: 250
Country: Canada
State/Province: NB
City: Fredericton
Lascar77 wrote:
no that is a myth duckster, you cannot deny what has been in use for like a few hundred years. Remember when big bikes knew standard chains and not o-ring. You cannot just simply say non o-ring is death kind of nay saying. Racers still use non-oring up to 300cc to trade power for longevity. sprocket and chain change half of a 520 mileage is ok for me for some performance gain and from what i see you completely misinterpreted what D.I.D is saying.


OK It's not a myth, and I'm not denying anything. DID do not recommend the use of 428 chain on anything bigger than a 125. Please have a look at the following chart lifted directly from their website. They also say that if your bike came with O-ring chain it should be replaced with the same of at least the same tensile strength. These are their recommendations, not my opinion or an urban legend.

Image

And although it has certainly not been a "few hundred years" many much larger bikes including a couple that I have owned and presently own do use non O-ring chain. Until the 1970's there was no such thing as O-ring chain, but it was developed to give satisfactory reliability and service life for the high horsepower bikes that started appearing in the '70s. In those days we used motor oil in some cases dripped automatically on the chain to lube it. Oily Chains attracted grit and dirt, and the rear wheel of the bike and your clothing collected greasy dirt with the oil that was slung off the chain. O rings provided a way to use sealed in grease to lube the chain internals while dirt was sealed out. Rollers and sprockets are externally lubed with proprietary waxy compounds that don't attract much dirt.

You can, of course, use a smaller chain to extract the last bit of maximum horsepower out of your engine. As speeds increase above 60 mph, HP required to maintain a speed is roughly proportional to the square of the speed. An additional 1/2 HP at 79 MPH might get you up to 80 MPH.

_________________
2004 Honda Rebel 250
2003 BMW K1200GT
2004 BMW R1200GS
1996 Ducati 900SS
1973 Norton 850 Interstate
1968 Triumph Bonneville


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Mon Apr 09, 2018 10:37 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
Indeed as you say they are recommendations and not an absolute "no". Where i come from we don't have cruise speed roads that much, the reason i want to try out 428 is to max the power on low end and pickup mostly. Most bikes in my country also still use the standard chains with higher wear rate and more maintenance so we are very much used to this.

The few hundred years part was just a figure of speech to emphasize that standard chains are still good and must not be discarded because of advice on newer type of chains, technology has advanced to give advantages definitely but sometimes my case is just one of those things that asks to be experienced first-hand as a rider.

however nowadays it would seem that there are not many that still dabble in rebel modifications enough to provide more input. I really appreciate all the feedback so far, i will probably try the 428 setup with a higher gear sprocket.


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Mon Apr 09, 2018 2:00 pm 
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Joined: Feb 23, 2009
Motorcycle: Rebel 250 plus a few others
Rebel: 250
Country: Canada
State/Province: NB
City: Fredericton
I'd be curious to get some feedback from you on the results of you conversion. ie do some acceleration tests with the stock chain and then with the smaller chain so we can compare numbers. That is the only meaningful way we can evaluate your mod.

_________________
2004 Honda Rebel 250
2003 BMW K1200GT
2004 BMW R1200GS
1996 Ducati 900SS
1973 Norton 850 Interstate
1968 Triumph Bonneville


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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Mon Apr 09, 2018 2:01 pm 
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Joined: Oct 16, 2005
Motorcycle: 2014 CB500XA
Rebel: None
Country: USA
State/Province: AZ
City: Green Valley
Let us know how it works for you.

_________________
John, 2014 CB500XA (Daily Rider), 2009 CRF230L (L'il Red Piglet), 1989 NX250 - sold, 2001 Rebel - sold; first bike was a gently used 1958 Matchless G2 (250 thumper)
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 Post subject: Re: CMX250 Sprocket Conversion
PostPosted: Tue Apr 10, 2018 9:44 am 
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Joined: Apr 6, 2018
Rebel: 250
Country: Mauritius
well rebuilding the bike, will take some time. if i do not forget about posting tests here you will see them. thanks


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