So about a month ago a friend brings me his 1994 300 4x4 that quit running. All it will do is backfire somewhat.

Did the usual checks and when I went to look at the crank seals, I noticed the problem.

The rotor/flywheel had sheard the woodruff key and had twisted on the crank throwing the timing off.

I didn't see anything else obviously wrong with the bike. The starter bendix seems to be working correctly and I don't think the rotor had ever been taken off the bike before.

The end of the crank and the valley the key rest in look to be fine, but the rotor was FUBAR due to the channel in it being deformed now. I found a cherry flywheel on eBay and ordered another woodruff key, put 'em on, and the bike ran like a top.

Fast forward to a couple days ago. The bike's back and doing the same thing. Sure enough, the key sheared again and this flywheel is FUBAR now.




I don't see anything obviously wrong with the end of the crank and cannot deduce a reason why this problem has occured twice now with this bike.

Anybody have an idea or experience with this issue?

 

Could be the shaft is worn down enough on the crank because the key could have ground down this area when sheared. I've had em shear in the past on 500's but not any others. Was flywheel nut installed tight enough? If not, could allow the flywheel to vibrate against key. I know it aint kosher,BUT I dont torque the flywheel nut,I impact em back on after I use blue loctite on the key and shaft threads. I dont advise using an impact because of what can happen,but its knowing when to stop that is important! After you replace with a new flywheel key and torque the nut,I would just zap it a little tighter allowing the flywheel to go deeper on the shaft which may hold it tighter. JUST a thought OPT