Hi Bob,

Your problem with the rotated brass bush can be fixed, I have done several of them for Aussie YS owners, and have not had one do it again.
I havn't worked out why this happens to to the odd motor, most of the ones I've repaired were new engines that would'nt start.

You treat the brass ring as a front bearing removal, the only differance is the crankcase has to heated up more.
And it is more critical to get the bush back into the correct position and aligned straight or it will be a real pain to reheat and remove again,
remember the crankcase has to be very hot, a good heat gun is a good tool to use for heating.

YS Service down under