Had to pull over on motorway yesterday, heard a screeching from what I thought was back wheel.
Got recovered home and upon stripping down I found this (I haven't touched it in the time I have owned 2006 400)

...have you found the nut?

Yes it was trapped behind the cover ( First pic, second pic shows damage inside cover)

Either the nut wasn't torqued correctly or the old nut & or washer was used. Using the old nut is not recommended. Using the old Bellfield washer isn't recommended either. They tend to be more prone to coming undone. They are regarded as 'one time use' items. Clean everything up & examine the crankshaft threads to make sure they are intact. If the nut was overtightened, the threads stretched or stripped, a common DIY error, the motor will need to be stripped. Do you know the bikes history regarding when the variator was last removed & by whom?

yes, had this exactly

when the person who installed the finned plat back on, they didnt have enough slack on the belt, so when the finned plate was on the shaft and was tightening the nut, it was tightening down on the belt. then slowly it got loose. had the same thing with 2010. known issue.

I drilled a tiny hole in the crankshaft and installed a cotter pin.

look in this video and see how he pushes the belt into the clutch so you have tons of slack. really nice technique, Ive used it many times now with success..



goto the 16min mark. foot holding belt, variator with both hands, and while you lift the variator (holding the belt with the foot), one hand turns the plate while lifting up. then watch how he holds the belt and clutch as he slides it on the rear shaft. he squeezes the belt.

I give him credit for the technique but no points for not taking the clutch apart to clean and regrease. so that means it needs to go to 36000km before it gets cleaned and regreased inside. not good. no grease will hold that long.