Rear sprocket runout

indyblue · June 22, 2012, 07:47:16 AM

My chain goes from very loose to very tight when rotating by hand so that I need at least 1.5" of slack to keep it from being too tight and I don't want to risk drive shaft/sprocket problems. I don't detect any unusual wear on the teeth and it appears as if the sprocket is not "centered" on the hub.

What should I check? Can the cush drive be worn/out of shape? The chain is not very old (according to the original owner) and the bike has only 39000 miles on it.

soundmindryan · June 22, 2012, 08:11:37 AM

By saying the chain is "not very old" means the p.o. didn't really know HOW old it was. It's the chain. Mine was like that at about 18k and when going down the highway, the bike felt like there were gremlins flapping my throttle back and forth so the bike would surge like the vibrato on an opera singer. Replaced the chain and both sprockets and everything turned to silk. Besides, even if your chain had been replaced, do you know what quality? FJ's eat cheap chains for breakfast.

Pat Conlon · June 22, 2012, 09:40:51 AM

I agree with Ryan. Replace your chain. Buy a high quality chain. With the chain off the back sprocket, spin the tire, does the sprocket run true? Or does the sprocket wobble? If it wobbles then you have other issues, like the carrier hub bearing. You know that the FJ sprocket is offset, right?

FJmonkey · June 22, 2012, 09:30:07 PM

Sounds like the classic stretched chain from an attempted wheelie on a cheap chain. Tight, loose, tight, loose.......

bcguide · June 23, 2012, 01:23:51 AM

It does sound like you chain is gone but check your front sprocket It wears the fastest and should be changed at lest once in the life span of a chain

RichBaker · June 23, 2012, 02:34:12 AM

Quote from: bcguide on June 23, 2012, 01:23:51 AM
It does sound like you chain is gone but check your front sprocket It wears the fastest and should be changed at lest once in the life span of a chain

Never heard that one before.....

bcguide · June 23, 2012, 03:16:21 AM

If you are having fun with the throttle the front sprocket will start to hook then the chain starts to stretch. If you change the front early thie chain seams to last longer

andyb · June 23, 2012, 08:23:16 AM

Based on my current chain and sprockets, with over 150 passes at the dragstrip, I don't agree. The chain is starting to wear, definitely, and the sprockets show wear, but it's pretty even all around. Partially that's helped by buying good chains to start with, though.

yamaha fj rider · June 25, 2012, 09:06:33 AM

Chain going loose then tight is worn out replace chain and sprockets they wear as a set. Worn sprockets wear out new chains. Hope this helps?

Kurt

soundmindryan · June 25, 2012, 10:19:35 AM

I replaced both chain and sprockets. I just thought they's all be evenly worn out but when I took off the sprockets and compared them to the new ones they weren't worn much. Probably could have kept them on but since the greatest expense is the chain itself and the new sprockets are relatively cheap, even for good ones, it's a no-brainer. Replace all as a set. Besides, I don't do wheelies or drag strip runs. Just frequent Kookaloos and normal commuting, rain or shine. BTW. It's supposed to be 108 today. Time to break out the soaked long sleeve shirt. Works great under my mesh jacket and pants.

axiom-r · June 25, 2012, 12:10:31 PM

Quote from: yamaha fj rider on June 25, 2012, 09:06:33 AM
Chain going loose then tight is worn out replace chain and sprockets they wear as a set. Worn sprockets wear out new chains. Hope this helps?

Kurt

And the opposite- if you put new sprockets on with a worn chain they will not be lasting long....

tim

indyblue · June 30, 2012, 02:54:44 PM

Finally got around to getting on here to reply, thanks for all the suggestions.

I cannot visually detect any wear on the sprockets, but when I spin the rear wheel by hand I do detect some "wobble" on the sprocket. It looks like it is out of round or not centered on the hub. What can cause it to be off center? There is no play in the wheel so I doubt it is bearings and the hub itself doesn't appear to wobble at all, just the sprocket.

How could the sprocket be off, what is it mounted to (looks like what yamaha calls the clutch hub - is that what is referred to as the cush drive?)?

I guess a teardown of the rear wheel is in order to check the components.

andyb · June 30, 2012, 10:02:54 PM

The carrier floats a fair amount. It's coupled to the wheel with some rubber bits. Odds are they've shrunk, worn, etc. Pull the wheel off and spin the sprocket carrier with the axle stuck through it. It's not unheard of for sprockets to have horrible runout if they're made poorly.

yamaha fj rider · July 02, 2012, 08:06:42 AM

Sprocket out of round very unlikely. Check your hub and wheel bearings? I worked in motorcycle shops parts department for over ten years and do not recall a sprocket out of round ever. Hope this helps?

Kurt

jscgdunn · July 10, 2012, 07:35:34 AM

Quote from: yamaha fj rider on July 02, 2012, 08:06:42 AM
Sprocket out of round very unlikely. Check your hub and wheel bearings? I worked in motorcycle shops parts department for over ten years and do not recall a sprocket out of round ever. Hope this helps?

Kurt

I had same issue. Check the front sprocket. It has a plastic "inner rim" than the chain actually rides on. On mine 3/4 of the plastic was gone...thus loose, tight loose, tight. Randy has a great deal on brand new OEM front sprockets. Pick the smallest rear you can....Seems like Yamaha forgot to add a 6th gear! Do chanins really stretch? Or do compopents suffer wear and hence chain loosens?

Jeff

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Rear sprocket runout