So I sheared my flywheel key at the races a week and a half ago. I got the tapers remated with valve grinding compound and a new key in and the flywheel all back together. Everything fires up and runs but I'm noticing a pretty strong vibration in the motor when revved and the rpms are coming back down to idle. I noticed this when at the races as well on the first practice run I ran. Any ideas what could be the cause? Might this be my crank bearing journals having some play and is what likely caused my flywheel to shear? Thanks for any help as always was hoping to get a few more rides in this season before pulling the engine and sending stuff off to be ported and o ringed this winter. Thinking now I may be sending the entire motor off though.

the counter balancer has a key also in which I sheered and my motor vibrated like a mutha!

My bike was doing thay. Double check motor mounts.

I checked motor mounts but I will recheck them again. We cranked down the suspension at the track with straps really low so it was almost rigid so I will check the frame for any cracks as well. I used an oem flywheel key. When it was shearing them after the rebuild I ordered like 4 of them. I had an oddball retaining nut on and now I have the oem nut with red loctite, I forgot loctite when I installed the flywheel last time.

I've had the timing / stator plate move off spec and burn thru some keys on other motors

Like jerry said ive never used locktite on my crank nut. I smack mine a few times with a dead blow them torque the nut.

Like I said I only used loctite because the manual called for it. Gonna check my motor mounts tonight but after they came loose last time and caused my bike to misfire and blow my reeds apart I loctited all the nuts on the bolts so if it's not loosr mounts is there a chance it could be my crank bearing journals? The flywheel key shearing is a symptom of something else and if it's not loose motor mounts is it possible for the crank bearings having play to cause the flywheel to shear or am I off base with that assumption?

The tapers fitting each other perfectly and the torque on the nut is what makes the flywheel stay put.  The woodrif key is there only for alignment when installing the flywheel.  The key IS NOT SUPPOSE TO HOLD ANY LOAD AND IS NOT DESIGNED TO KEEP THE FLYWHEEL FROM ROTATING ON THE CRANKSHAFT. 

Loose bearings or bearing pockets will not cause a flywheel key to shear.  Again....your tapers are bad or the torque is not up to spec.  It may be a simple as your torque wrench is junk and your not applying enough torque when tightening the nut.  Do not put the engine in gear and use the rear brake to hold the crank steady.  Use a spanner wrench to hold the flywheel while torquing the nut.

So will loose bearing pockets or bad crank bearings cause a vibration in the motor as the rpms settle down from being revved? Or am I looking at potential loose mounts or a **** frame more likely?

Nothing has changed with my carb setup it's pilot jetted for cold weather and I turned the air screw in when the temps dipped. Starts first kick, main jet was bumped from a 400 to a 420 when temps dipped as well.