I built this motor for my buddy Eric Swortsfigure in 1990 when we were both racing. His good crank fell off the shelf in the big 89 quake, we used another crank we had laying around.
It broke because when it was balanced at the factory, too much material was ground off the bottom of the flywheel weight so they needed to remove some from the top for balance. They used the same 1/2' drill, drilling a few shallow holes in the thin area between the journals, weakening it severly. It held up in a street bike but not at the track.
Eric was leading the race at Sears Point @ 120mph when it let loose, It destroyed most of the bike, blew a chunk into his leg (requiring stiches) and showered the followers w/ hot shrapnel . Ken Armann still has the engine for laughs.
I'm new to Nortons fourms, I've been riding, racing and working on them since I got my MKIIA in 78', but left them alone for years while I raced Ducatis. I've been fixing them up a little lately and came across this forum. The Newbies cracked me up w/their problems, prompting this post. I know everything about what fails on these bikes and how to fix them. Racing them played a big role in my career as a Mechanical / Reliability Engineer.
I've put up some old (and new, see the trackmaster) Norton stuff on my FB page (if you have access):
http://www.facebook.com/home.php?#/prof ... ef=profile
Can someone tell me how to upload photos here? I have more to share.
Tom