tompat3463
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| posted on 11/1/15 at 07:17 PM |
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chain drive sprocket wear issues
Hi guys, im building a front engined FWD mini and im have a few issuses where the chain is skipping on the diff sprocket. when I initially put the
chain and engine and all other drive parts togeth I tightened the chain very very tight. Now after a few very small test runs around the back field
the chain is very slack and the diff sprocket teech are worn (or rather the tips have been bent over forming a wave shaped tooth.
do all chains go slack straight away as this was a brand new chain
also, the diff sprocket was custom made from a guy or firm on ebay, ordered a 520 sprocket and I have 520 chain and gearbox sprocket but the gearbox
sprocket and the diff sprocket seem to romm with different pitches, its a very small amount but surely if the the teetch pitch are the same then if I
roll both sprockets along my bench by 10 teeth I should have the same distance with both.
is this correct or is it because the 13t is a much tighter radius is doesnt work the same as the 36t ??
any help could be great, thanks Alan
[Edited on 11/1/15 by tompat3463]
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minitici
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| posted on 11/1/15 at 08:01 PM |
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A 520 chain/sprocket is 5/8" (15.875mm) pitch
520 is not the strongest chain you could use - 530 would be better as stronger chains are available.
530 conversion sprockets are available for most bike engines (What engine are you using?
530 sprockets are wider but same 5/8" pitch.
It does sound like you have miss-matched sprocket types/pitches.
I once came across a sprocket which was not correctly machined and the chain would not seat correctly - took a while to figure out what was wrong.
Chains should not be 'drum tight' but very short chains do not require the normal slack you would have in a bike installation.
13 tooth front sprockets are as small as I would want to go with short chain runs due to limited wrap around.
PM me if you need more advice or new sprockets.
Doug.
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tompat3463
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| posted on 11/1/15 at 08:09 PM |
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Thanks for the reply. I've messaged you.
One more note is that the chain has zero play laterally. It's new
It does seat in the large (damaged) sprocket perfectly. So Im thinking I just haven't had the chain tight enough and its just tried to skip and
bent the teeth over
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minitici
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| posted on 11/1/15 at 08:11 PM |
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Another potential problem area which causes the chain to slacken is movement between the engine and differential.
It takes a very small movement to make the chain slack.
If there is any rubber in the engine mounts then this can be enough to cause problems.
I have seen several installations where the engine and/or differential mounts and frames have physically bent under acceleration.
The owners were forever tightening their chains - sure sign of a problem!
Finally, if you tighten the chain then rotate the sprockets throughout their entire rotations and the chain goes tight-loose-tight then you could have
problems with eccentricity of the sprockets or a section of damaged chain.
Last season we were chasing such a tight-loose problem and it turned out to be a bending/cracking output shaft on the gearbox
(output shaft eventually failed and replacement cured the problem).
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sickbag
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| posted on 11/1/15 at 08:21 PM |
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My CBR600 had 525 as standard but to cut weight and friction changed to DID 520 chain and sprocket set for racing. Rear sprockets started to wear
after about 50 laps of Donington but chain was OK for another 50 or so. I think for the extra weight, etc, of a mini I would use 530 chain set.
Finally back on the job!
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MikeRJ
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| posted on 11/1/15 at 09:34 PM |
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quote:
Originally posted by sickbag
My CBR600 had 525 as standard but to cut weight and friction changed to DID 520 chain and sprocket set for racing. Rear sprockets started to wear
after about 50 laps of Donington but chain was OK for another 50 or so. I think for the extra weight, etc, of a mini I would use 530 chain set.
I fully agree, a 520 is too narrow for a BEC, the tooth loads will be very high.
I also worry about the phrase "I tightened the chain very very tight.". A chain absolutely should not be very, very tight. Waiting for
the "diff bearings have failed" thread in the near future!
[Edited on 11/1/15 by MikeRJ]
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tompat3463
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| posted on 11/1/15 at 09:38 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by sickbag
My CBR600 had 525 as standard but to cut weight and friction changed to DID 520 chain and sprocket set for racing. Rear sprockets started to wear
after about 50 laps of Donington but chain was OK for another 50 or so. I think for the extra weight, etc, of a mini I would use 530 chain set.
I fully agree, a 520 is too narrow for a BEC, the tooth loads will be very high.
I also worry about the phrase "I tightened the chain very very tight.". A chain absolutely should not be very, very tight. Waiting for
the "diff bearings have failed" thread in the near future!
[Edited on 11/1/15 by MikeRJ]
u
How very helpful
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coozer
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| posted on 11/1/15 at 10:00 PM |
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If you look at motorcrossers you'll see they run the chain pissy slack with rollers and guides to keep it on track, is it worth adding a roller
just in front of the drive sprocket ( underneath)??
1972 V8 Jago
1980 Z750
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motorcycle_mayhem
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| posted on 12/1/15 at 07:46 AM |
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As has been said 530 is what you should be using. Real Japanese HD/Race chain - NOT a Chinese Ebay copy.
Extreme examples, some of the tuned Hayabusa hillclimb single seater slick-shod cars run a double row 530 chain(!), even 630 gets used. Overkill on a
road thing.
I suspect your mini (with everything probably so compact around the engine/diff) has a high angular chain run, minimal sprocket centre separation. Not
good ingredients for chain life, neither is a 13T on the engine, but space compromises are always there at either end.
Modern chains don't stretch much, don't wear much, but will break eventually. Extreme tension will break a chain quickly.
OK... so go 530 and reassess.
For Sale:
If you want to continue to explore a 520 for some reason, I do have a brand new genuine EK 520 race chain, a comprehensive selection of new Suzuki 520
sprockets 13-18T and commensurate rear 48-50T rear Mini differential sprockets. All pitch matched, in excellent health. This was the fitment on my
600cc Jedi racing car, now unwanted as I'm running 1000cc.
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