It pays to go over everything when re-building

[cturek]

I'm starting to put back together my 400 and, while torquing down the swing arm bolt nut, the end of the bolt snapped off! Looking at the end of the bolt that broke off, about 75% of the bolt was already broke! If I wouldn't have pulled the swing arm to clean and lube the bearings, I would have been riding with that defective bolt!

 

[hardtailed77]

DAMN!!! That may have caused a few problems at about 50MPH..........Glad you found it ahead of time!!

 

[drewpy]

apparently thats a common problem, the way yamaha cut the bolt and with it being hollow, it creates a stress point just behind the threads.
I've read in the German site that a suzuki GSXR solid bolt replaces the hollow one, but you need to first tap under the swing arm for a zerk fastener for greasing the bearings.
If I can find it post I'll copy it here.

It's 01:30 in the UK and I need to sleep