Here's another patient: mine has covered 70.000km's and hasn't had an easy life. Noticed a rather irregular rattle that distorted the idle run speed. My mechanic demonstrated how it disappeared when he put it in first gear, loaded up the drive by engaging the clutch while keeping the engine at low rev speed and brakes on => sound disappeared, so nothing wrong with piston, rod, big-end or crank or gearbox. Clutch dis-engaged: rattle returned => some sort of play in clutch (drive)

Took it out to find out it's exact the same problem as with Niek's bike.

HJ

If it is a loose right side primary drive nut then I suspect the r/h main bearing is worn.
As the bearing wears it not only develops radial play - it develops axial play. It's the axial play that unloads the nut.
Just retightening the nut helps to eliminate the play. I've been riding about 25k miles with another worn r/h main bearing by just tightening this nut (slightly over torqued).

Yeah, I've just been reading about rolling element bearings in main bearing applications, and it seems that any excessive radial play (from new) is adjusted by axial preloading of said bearings.

So RickM is right, according to guru type people. Retorqueing a loose crank nut should quieten a bearing if it hasn't been left too long.

I think I need to get a life...:005::gsmile:

Who was it that said a small amount of knowledge is a dangerous thing?

thanks for that guys. Briefed this on to my mechanic and he confirmed this (rather skilled/experienced guy).

HJ