Hi Dave, I have a 120SC which I purchased from a fellow club member, I have it in a DP Ultimate, It ran like a powerhouse for the first 6 flights. Today after the first excellent flight the engine wouldn't transition and would knock and kick the prop loose upon throttle up everytime. I would restart it and at idle I would notice bubbles in the line from the regulator to the carb and nowhere else, I also read in one of your posts that bubbles in this line was normal, but the engine was acting like it was very lean even after opening up the HS needle. also when I removed the regulator to check the diaphragm I forgot to notice which way the reg. sat on the engine. I'm pretty sure it's supposed to be on one way and not the other, like that nub facing forward. BTW the diaphragm didn't look bad but it was rough around the edges.

One more thing, The engine came in an SC box, but looking at the exploded view of the FZ it's regulator is of the same type with the plunger sticking in under the diaphragm.

Thanks
Frank A Rega