Hi Dave,

This is for a friend who has a YS 91ac with problems:

1. Engine has no transition, moving from idle to full throttle takes a good few seconds before it runs at full rpms.

2. Idle is extremely rich.

Regulator, valve etc have been dismantled and checked for debris.

It is an older model and may not have the gas port mod I have seen mentioned, would this solve the above problems ?

Thanks,

L

If the problem is leakage past the piston, it will. I think it is best to send it in for service.