Hi sparker, what sort of blade carrier does it have, I bet it has a bar and my belief is they don't give enough spinning weight and so much inertia is required on the keyway to help it spin. The other issue is the key should not be taking that much load, it is only so the timing can be set. My gut feel is there is a problem with the taper and it is not being tightened down hard enough on the taper. It may require a bit ground off the inside of the wheel to allow it to come down just a fraction on the taper, doesn't need much
