Chain came off during a turn...

This happened on Sunday afternoon as I came off the highway. I was making a left when the light turned green and about halfway through the left I felt the rear lock up and start sliding out. I kicked down my left foot as hard as I could and managed to straighten the bike up as it skidded to a halt. Got it off to the side of the road and then started looking it over.

At first glance I thought it was a chain issue but I wasn't certain as it had been adjusted and lubed a day before and didn't have any stretched out sections. Now that I've had time to take it apart it seems like something got in behind the cover and broke a small piece of the casing which would have gotten caught between the chain and front sprocket causing it to jump off and then the same effect would be seen in the rear, similar to switching gears on a mountain bike.

My question is this: aside from the obvious things to replace such as the sprockets, chain, nuts and studs on the rear is there anything mechanical I should be worried about? Also, the seal behind the front sprocket had a sliver taken off, something worth replacing or is it a non-issue? The seal in question is #32 in the exploded diagram linked below.

http://partsfinder.onlinemicrofiche...&make=yamahamc&a=364&b=18&c=0&d=-TRANSMISSION

ashrafnisar said:

This happened on Sunday afternoon as I came off the highway. I was making a left when the light turned green and about halfway through the left I felt the rear lock up and start sliding out. I kicked down my left foot as hard as I could and managed to straighten the bike up as it skidded to a halt. Got it off to the side of the road and then started looking it over.

At first glance I thought it was a chain issue but I wasn't certain as it had been adjusted and lubed a day before and didn't have any stretched out sections. Now that I've had time to take it apart it seems like something got in behind the cover and broke a small piece of the casing which would have gotten caught between the chain and front sprocket causing it to jump off and then the same effect would be seen in the rear, similar to switching gears on a mountain bike.

My question is this: aside from the obvious things to replace such as the sprockets, chain, nuts and studs on the rear is there anything mechanical I should be worried about? Also, the seal behind the front sprocket had a sliver taken off, something worth replacing or is it a non-issue?

Click to expand...

I would replace that seal. If it's not trouble now it will be later

BTW, thanks to the rider on the white R1 that signaled with a thumbs up to see if I was okay or in need of help as every other rider that spotted me just rode by. Had a few cars stop as well, good on them.

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Check for any deflection on the output shaft, make sure its not bent. Also closely check your cases for any cracks in there. Hopefully you get off lucky with just a sprocket and chain!

happycrappy said:

Check for any deflection on the output shaft, make sure its not bent. Also closely check your cases for any cracks in there. Hopefully you get off lucky with just a sprocket and chain!

Click to expand...

How would I go about doing that? I have a rough idea what I'd be looking for but am a little lost as to the actual process. Thanks in advance.

I would imagine rotating the shaft would make it clear if it was bent. There would be a wobble to it.

As for cracks in the casing, if the cases are dirty clean them up with degreaser and inspect carefully by eye.

ashrafnisar said:

My question is this: aside from the obvious things to replace such as the sprockets, chain, nuts and studs on the rear is there anything mechanical I should be worried about? Also, the seal behind the front sprocket had a sliver taken off, something worth replacing or is it a non-issue? The seal in question is #32 in the exploded diagram linked below.

Click to expand...

If it's not leaking, don't worry about it. The beauty of chain drives is that they take all the damage, so it sounds like you need a chain, but if the sprockets aren't damaged, they should be ok.

ashrafnisar said:

How would I go about doing that? I have a rough idea what I'd be looking for but am a little lost as to the actual process. Thanks in advance.

Click to expand...

If you can get the bike up on a rear stand, just spin the wheel with the chain installed and watch the out put shaft for movement up and down.....The chain actually does NOT take all the damage; seen plenty that argue the point considerably. The lack of space around the countershaft sprocket is surrounded by an aluminum case, so debris or the chain itself can bind in there and destroy everything. Not saying this the case for you, but as it was mentioned elsewhere, clean the area very well and inspect for oil leaks, give it a spin while on a stand, and cross your fingers! Just saw one a couple weeks ago where the chain broke, and promptly annihilated the engine as a result.

So far I'm not seeing any leaks, casing appears to be okay other than the piece that started this whole thing in the first place. On second thought, that seal looks a little worse than I originally thought so definitely gonna end up replacing it. Looks like the chain gouged some of the metal around the seal so I'll have to smooth that out before touching the seal itself.

Fired it up tonight, no issues with the motor, shaft spins slowly in neutral and I'm not seeing anything out of the ordinary just by eyeballing it. Didn't throw it in gear, not sure what held me back but I just want to deal with everything else first.

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happycrappy said:

Just saw one a couple weeks ago where the chain broke, and promptly annihilated the engine as a result.

Click to expand...

Sounds like the chain took all the damage.

Totally forgot to come back to this thread after I got the bike back on the road. Good news is no issues after swapping everything out for new. Bad news is I despise the -1/+2 sprocket setup I opted for. Going to return to a stock rear sprocket next season.