I have a problem (besides the obvious)
I am in the process of rebuilding a MC21. Its all together, registed and rideable
Since the bike sat for about 3 years,the chain was rather orginary. WHen i started riding it again. It had developed a noise that i thought was the old chain just complaining.
Basically, under power or light throtle,its fine, all normal. But as soon as you shut the throtle and start decelerating, a whirring chain sound starts. I have installed a new chain thinking it would go away. Its still there. I have had other people check tention, and that it fine. Ive tried running it a bit tighter, and looser. Doesn't change. I though that the gearbox oil might be old. Changed that (dry clutch), ITS STILL THERE. I cant think of anything that would cause this noise only on deceleration, but not on acceleration. Seems its fine when the front sprocket it driving the back. WHen the back drives the front - noise. . . . . . Any ideas NSR guru's ?
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Is the noise related to engine speed road speed, or which gear you are in? You may need new sprockets as well. Normally when the chain is worn out so are the sprockets.
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james
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Yep, it will be the sprockets, more speciifcally the front sprocket teeth being so "hooked" the chain tries to stay on as it runs off the bottom of the cog.

You may have found it even got slightly worse with the new chain as the old one would have had worn pins that allowed it to drop off the hooked teeth more easily.
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Cam chain tensioner going slack on the over run I think...
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Dave Ett wrote:Cam chain tensioner going slack on the over run I think...

Evil Dave...
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Dave Ett wrote:Cam chain tensioner going slack on the over run I think...

Very nice, like your style. I might need to reshim the exh valves too

I was hopeing not to have to pull the fairings off to get to the front sprocket, as its a bitch with these cheap arse fiberglass fairings i have.

I changed both front and rear simultaniously last time. Rear is still good.

Thanks for the help. I shall get a new front cog.

Just on the off chance, there is no way this could be a gear box related problem ?
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Winning isn't everything, but loosing isn't anything

sounds more like your exhaust bearings to me

Flux capacitator might be on the way out as well
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just thinking i mite be your dip stick rings going

i had a similar noise when i first rode mine it tured out to be just the sound sticking brakes

fontyyy wrote:Yep, it will be the sprockets, more speciifcally the front sprocket teeth being so "hooked" the chain tries to stay on as it runs off the bottom of the cog.

You may have found it even got slightly worse with the new chain as the old one would have had worn pins that allowed it to drop off the hooked teeth more easily.

Yeah i've found that i go through front sprockets much faster than rear ones. I figure it's due to the size difference, the front does 2-2.5 revolutions to every 1 of the rear, so i'd assume it should wear out about that many times faster. last time i changed the sprockets on my 600 road bike (with a 525 chain), the rear looked nearly new but the front had substantial hooks on it. I replaced both anyway.

Speaking of sprokets, what's the stock sprockets for the MC21, 15/40? And any one know how many links should there be in the chain? (i couldn't be bothered counting them)
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bj wrote:
Speaking of sprokets, what's the stock sprockets for the MC21, 15/40? And any one know how many links should there be in the chain? (i couldn't be bothered counting them)

Info easily found in the Online Parts Manual... I couldn't be bothered to type it.
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117 links to my chain.

I just did this exercise when fitting mine last week
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Hang on. Might of been 107. Hell, i cant reember
Just checked the left over. 107 plus link sorry.
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Winning isn't everything, but loosing isn't anything

Finally got around to fitting my new front sprocket. And guess what, it wasn't the problem

Pull cover off, all teeth look good. So i play with the tention of the chain, thinkin that it must be hitting something to make the noise.
And it was
Unbeknowen to me, there is a bracket, that runs from the swing arm to the gear box (to stop engine torque movement is my guess). Attached to the swing arm, yes, gear box . . . . so its hangin down, and rubbing agaisn't the chain off throttle. Under power, the bottom of the chain must be just loose enough to just miss it.

Anyone got a spare bolt lying around ? LOL
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