Dave,
Just got it back from service after waiting 6 weeks. this was after having it back from service a time before and having identical symptoms show up about two weeks later. First I apologize for being bitter. I just got back from the field and I'm really dissappointed. The 63 is still loading up during certain maneuvers but nothing regular. For example sometimes midflight I'll throttle up from 1/3rd throttle and it will take 30 seconds to reach peak rpm. Almost lost my plane tonight doing that. Then later in the same flight after doing the same maneuver that loaded it up before (harrier) it transitioned lightning quick and was screaming, like it should. It's also detonating which it never did for the first 5 gallons for fuel. To refresh you, this engine was nothing but perfect for about the first 5 gallons. club members even went out and bought YS engines because they were sold on my relaible YS63. Then it started loading up on flat spins. Then I sent it in and they replaced the regulator. Well it started again and they again replaced the regulator and put a gasket set in according to the service slip they shipped the engine back with. I don't get it. I've already missed a lot of flying waiting for this to be fixed and it wasn't. I've got a very bad taste in my mouth about YS engines. I'm so close to giving up and buying something else. Yet in the back of my mind, I know this engine can run perfectly.

For what it's worth I'm running a Zinger 13x5 prop, peak rpm this evening was 11,400 rpm. Cool Power 30% heli fuel. Idles reliably at 2000-2100 rpm. New OS type F glow plug. Valves adjusted to .003". Before i did anything I set up the engine to factory settings and used the run instructions on the YS website. What do you think?

Mike