I tried it out again and to my dismay... it was still strange. It just wouldn't settle down. And at higher rpm (had to run it a little higher rpm at times to prevent it from stalling) it had a light but sharp mechanical clanking that scared the heck out of me. I have since replaced the ys with a .61 Tiger Shark engine. Upon removing the engine, I realized that there was a leak from the fuel line. Also, the dubro kwik fill fuel valve may have an air leak. Would this explain my ys63 "idling" at 5000+ rpm or that clanking sound at higher rpm?

On a completely different note, I moved from using cosmo aerostar 23 to coolpower 20 on my OS FS30 and can I say that the power differential seems quite startling? Idling, especially has required much more throttle to maintain. Is that normal?