My simple Front Sprocket Fix

[Dead Eye]

I forget who, but someone did post up that this is exactly why the nut fails. Its due to a manufacturer defect where Yamaha failed to produce output shafts of the correct diameter. I can't remember the exact sizes at the moment, but anything less would cause the threads to strip / skip etc causing the nut to eventually fail. Correctly sized output shafts typical have no faults at all from what I've gathered.

Mine torqued up to 90Nm the other day with no issue or iffy feeling so its definitely worth keeping an eye on yours. Also, I believe 70Nm was originally recommended for the old nut, but Yamaha revised this to 90Nm for the new 12mm nut