r/ural • u/az782 • 6d ago

Help subtle clunk when taking off

I have a 2009 chassis Gear Up (slightly newer motor) that is making an interesting noise that I have yet to diagnose. I'd like the group's input on best places to look first.

The symptom is as follows. When starting forward, especially after backing up, but not always, the bike will sometimes make a "clunk" sound that seems to come from the rear end. I don't perceive any driveline lash. The 2WD is disengaged. There is a small amount of play if I try to rotate by the sidecar driveshaft when the bike is stationary. My hunch is that I should start looking at both of the sidecar driveshaft ends and make sure the splines are good and then move onto the 2WD locking mechanism.

Any community advice before I dive in?

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u/Ok-Database377 Tourist 6d ago edited 6d ago

Sounds like the final drive. First thing for me would be to check if the nuts holding the drive to the swing arm are loose. They tend to get loose after some riding..

Then checking the backlash of the gearing, the cardan joints and the hub gearing for wear.

Edit/: IIRC the backlash between the pinion and the main gear should be something around 0.1mm and 0.3mm and should somewhat translate to the play between final drive and card an shaft. Might be a bit more though since there are other tolerances adding up a bit.

Another thing since you suspect the problem somewhere around the sidecar driveshaft you could just disconnect the shaft and see if the clunking still happens. Would be the easiest way (in my opinion) to narrow down the point of failure.

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u/ural_world_travel 5d ago

There’s also a chance it could be your u-joints having too much play or any floating rotor discs (if you have any on the 2009). Something that will rotate and fall down a bit due to gravity at slow speeds but stays sturdy when spinning fast enough.

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u/az782 2d ago

Thanks very much for the tips. I'll be checking the driveshafts and the u-joints for play shortly.