On my carter 150 it keeps shearing the key at the flywheel that the starter gear slides over. I have replaced it 2 times so far and about to tear it down for the 3rd time. The only major mod is an a12 cam so I cannot figure why it keeps breaking the key. It is about a hr and half to 2 hr fix and I am getting tired of digging into it. I am happy it ran all day friday and over half the day saturday at the bash but it is getting irritating. Any ideas what is causing it to keep shearing?

If you're shearing starter clutch keys, maybe the starter clutch is not releasing once running.

Make sure the crank key way for the key stock is not damaged and causing the key to rotate over on its side.

Mike if you can take a picture of what your talking about it would help.

Mike ,thos metric starter keys are junk!They only go into the stater clutch about .02.Once they shear its hard to work again.The keyway in the crank is probably bad now. File it out square and fit a standard woodrift key.

x2