Thanks for the YS tips. I do believe in every one of them. My problems with the 91 was with the 'around' idle adjustments. I ensured my throttle connections were rigid, with ball links on both ends to ensure smooth operation.

It would either idle really high or really, really low then quit. There was no in between. I haven't touched the regulator screw or the carb opening amount since it was new (and running good initially). Replaced all fuel lines.

I know YS are great engines. Personally, I like OS and Saito for everyday 4-strokes. I just want to fly more and tinker with engines less.

I'm curious to see a flight report with the 91 FX or similar, so I look forward to it Will! I assume you are putting a pipe on it?

That's the other thing I was worried about - i already moved two elevator servos to the tail! THAT doesn't help if I get a 91FX.

thanks for all the replies.