All right, Bummed out to hear of so many sheared flywheel keys!! But hey, it's supposed to be the weak link in the chain. All the load on the flywheel is supposed to be thru the taper on the flywheel/crank and the key is there primarily to time the ignition. If in fact there is an unnecessarily high load placed on this system, the keyway loses...a good thing! Where the excess force is coming from and why can't the starting system absorb this force is the question. I guarantee if there are this many cases of sheared keys, YAMAHA will figure it out.