Just checked my front sprocket nut, and it's loose, despite the folded but of the washer still being tight against it
Worse it'll the nut will turn but won't unscrew

Guess I'm gonna have to cut it off (cut the last one off with a dremmel and a chisel), neaten up the thread, and hope it's not so badly damaged that a new one will hold. Anyone tried threadlock on them?
I must say this is sounding more and more like the same problem on the DRZ400, which suffers from a loosening front sprocket nut.
What happens on the DRZ, isn't the nut coming loose, as the tab washer prevents it from coming undone, but the very slight rocking back and forth on the splined shaft due to accelration and decelration, causes wear on one of the internal clamping faces behind the sprocket (inside the gearbox), which means a loss off clamping pressure, when it wears, and hence a 'loose' nut.
The solution is loctite 638 on the splines on the shaft, then put the sprocket on, and torque to 70Nm. This stops the sprocket rocking back and forth and hences stops the wear.
I have experienced this first hand and the loctite is a solution to the problem.
If the nut has come loose on your TDM, but the tab washer is still bent over, then the nut hasn't actually rotated and loosened. The only other thing that would cause a 'loose' nut would be wear between the clamping faces of the sprocket , oil seal spacer, bearing etc and hence loss of clamping force, which would allow the nut to be loose.
As tonski says, the normal loctite from halfords (blue 'stud locker' or red 'stud & bearing') is not strong enough. You need to get '638' from an industrial distributor
You will need a 3 legged puller to get the sprocket off when its time to change it
Edited by GuyGraham, 01 July 2008 - 05:33 pm.