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Discussion Starter · #1 ·
Hey all I have a 2006 Z750s with ~30k miles on it. Recently I started noticing a strange rattle/ vibration / shudder coming from my rear wheel specifically when I am starting from a stop. Ill let out the clutch slowly and usually the revs dip to ~1500 for a second and as I start to roll on I feel a shudder and strange vibration in the seat of my pants and the foot pegs. It gets VERY apparent if I am going up hill at low revs ( like starting from a stop going up hill) Im not bogging the engine and it will sometimes continue to around 2500 rpm then it kind of smooth out. It did not used to be like this and Im wondering what your thoughts are.

My chain tension is fine, the chain wear and sprocket wear are fine and the engine feels just fine when in neutral. I have a suspicion that it could be the rear wheel bearing, is that possible?

Thanks!
 

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I'd pull that tire off and have a good looking at the cush drive (those rubber thingies behind the sprocket). You can check your bearings too.
 

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Discussion Starter · #3 ·
Yeah thats going to be my project tonight. I was just looking for some suggestions of things to check out. The cush drive is a good idea!
 

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Could be swing arm pivot bearings as well. Give your shock links, and bolts a good look over to make sure nothing is loose. Seeing that you said the chain tension is good I'm assuming the chain alignment is also good, and straight?
 

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My chain tension is fine, the chain wear and sprocket wear are fine
How many miles on the chain ?
Have you adjusted out any extra slack lately ?

It is almost impossible to gauge the health of a chain just by eye while it is still ON the bike.

Have you spun the rear wheel while it's off the ground ? Often that will tell you a lot.
 

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The Kawasaki cush drive rubber things (that may not be the technical name) are not very high quality. I'd replace them. They are semi costly for chunks of rubber, but i'll bet you have to get new ones.
 

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My cush drive bearings went out at about 30,000 miles. Same symtoms and an easy fix. Just manually rotate the bearing when you get the cush drive off and it's pretty obvious if thats the problem. Spin the wheel bearings the same way to check them. They should rotate without any sign of roughness or crunchiness, (is that a word?). If you have any doubt replace them.
 

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Discussion Starter · #8 ·
I am unsure of the miles on the chain and I took the whole wheel off the otherday and I do not have a chush drive. The sprocket is bolted directly to the wheel. Its a Z750S. The chain seems to mesh with the sprocket well. Im not really sure where to look. My bearing are sound and everything else seemed Ok. Whats the correct procedure for setting chain slack?
 

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The sprocket will come off the wheel with a little wiggling, cush drive will be behind it.

Here's a free pdf manual for you, it'll walk you through the chain slack question. Safe download, it's where I got ours: ZR-7 and ZR-7S Maintenance Manual Backup | jadz
 

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I'm not sure the z750s has the same rear end as the zr7/zr7s. The manual may not apply.
 

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DOH. My bad for not reading clearly enough. Luke, search for Z750S pdf manual and I bet you'll find one.
 

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From what I can find the 2006 Z750s does have a cush drive. Lay the wheel flat on something soft like a carpet so as not to damage the brake rotor and grab the sprocket on each side and wiggle it up and down while pulling upwards and it should seperate from the wheel. The cush drive bearing is on the inside of the part you pulled off. Try and find a manual if you can.There are bearing races and spacers so make sure you get them back in right when you put it back together.
 

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I have an '05 z750s, and yes it has the cush drive. It appears the sprocket is bolted to the wheel but if you wiggle it back, and forth it will come apart, and the 4 rubber "cushions" will be right there.
 

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So the cush drive seems to be okay but the noise is getting worse. I'm not sure what to do
Odds are excellent that it is a worn out chain/sprockets.
Seek help from a professional......that is, make a shop appt.

Even experienced mechanics sometimes have trouble identifying a worn out chain.

What about lube; how often do you lube it ??
 

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You have been messing with this without results for a long time. Obviously, (no insult intended) you need help. Take it to a dealer or post what city you are in, maybe there is a member who lives close that could help. If you have checked the bearings and the cush drive I would go along with the idea it could be the chain and/or sprockets. It's hard to analyze a problem through the net. Good luck to you, don't get discouraged.
 

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Discussion Starter · #17 ·
You have been messing with this without results for a long time. Obviously, (no insult intended) you need help. Take it to a dealer or post what city you are in, maybe there is a member who lives close that could help. If you have checked the bearings and the cush drive I would go along with the idea it could be the chain and/or sprockets. It's hard to analyze a problem through the net. Good luck to you, don't get discouraged.
I agree that I should bring it to a shop, Ive been kind of putting it off because the riding season is pretty short for me so I kind of designated this as a "winter project" and ive been putting off really tearing into it! Im fairly certain that a new chain and front and rear sprockets will sort it out. Any advice of where to get chain and sprockets?
 

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Discussion Starter · #18 ·
So the front sproket is very worn so im going to replace the chain and front sproket. Does anyone have any experience with dropping a tooth? would it be worth it?
 

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I can't speak to dropping a tooth on the z750. I know on my zr7s I went with one extra tooth. It dropped the revs and increased fuel economy.

Dropping a tooth will make the bike a little peppier off the line, you'll have to shift a bit sooner, and fuel economy will go down.
 
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