Dave
Thanks for the fast response. I evidently made some incorrect assumptions with the limited (incorrect) information I had when I tried to set the engine. I actually managed to get an on-line copy of the manual for the engine and things are clearer now!
http://www.ysperformance.com/
Because of the plane I am flying, I would rather use the 11 x 6 prop but I won't try it again without at least 15% fuel. If it won't turn a little faster and run cooler once I manage to get the fuel mixture set right, I'll drop to a 10 x 6 or 10 x 7 as per your recommendation. Does this engine need the higher oil content of the 20/20 fuel if I'm not running very high RPM ? - the Omega is (I think) 18% oil with some castor.
I don't know what plug is in the engine but I'll pick up an OS #8 and give it a try.
Are there any modifications to reduce backpressure for the stock muffler (i.e. drilling out baffle)? Would this just increase noise with little additional benefit?
I really appreciate the assistance and I'll let you know if I succeed.
Ross