Louie; If you are talking about the Teflon button that goes in the crankshaft, they are held on by the back plate. The part that goes into the crank is long enough that it won't come out. Its main purpose is to keep the steel crank from wearing on the back plate.

Louie; I think yours are OK. They originally are very thin and flat. McCoy Red Heads have quite a bit of play fore and aft in the crank, and unless they have had an electric starter used on them, the button does not even wear on the back plate. The crank is always pulled forward with the prop.

The crank is always pulled forward with the prop.

And the rod tends to migrate backwards to the back plate primarily through crank pin flex and secondly through the intake charge being directional.

The best fix for this problem, if indeed it is one, is the use of a hardened steel disc attached inside of the back plate.