Diagnose a cush drive fault

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Q. I have a 2005 Yamaha Dragstar 125 with 3000 miles on the clock and I have excessive free play in the drive system when throttling off.

The engine goes from driving the bike to the bike driving the engine (on overrun), so I end up sort of kangaroo jumping in first gear.

When I’m stationary I can rock the bike forwards and backwards about a foot.

The chain slack is correct at just over an inch, is there any adjustment in the gearbox where this lost motion can be taken up?
Jerry, MCN forums

A. The problem and the solution are at the other end of the drivetrain, in the rear wheel hub. To check it is that area, put the bike in first gear with the engine off, let the clutch out and see if you can rock the rear wheel backwards and forwards.

If that’s the case, you’ll need to take the rear sprocket off.

Then you’ll see it slots into the wheel hub between rubber sections that look like slices of cake. They are cush drive rubbers and are designed to absorb the shocks to the system when you come on and off the throttle.

It’s unusual for them to be worn this early in the bike’s life, but if the chain has been run very slack that will accelerate the wear.

They simply push into position so they are easy to replace.

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MCN

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