I had a used G-38 on the shelf for about a year. Needed it for a new plane. After install found that I must have the High Speed needle all the way closed (spring totally colapsed) for the engine to develop max RPM. I am only getting about 7000 with a Zinger 18-6x10. Thought I was getting more like 7300 before. Acceleration seems fine. I also switched back to the Stock muffler that came with the engine - could this be causing the lose of power???? Any thoughts on this one folks???

I have another G-38 and was thinking of swaping carbs to see if I saw a difference.

Thanks for any assistance.

The old G38 carb (WTA6) is designed to be run with the high speed needle adjusted from closed to 1/4 turn open...There's a small brass plug over the high speed needle with a small hole in the center..With the needle closed there is still enough fuel going through the hole...

The stock muffler is your problem too. These engines are very sensitive to backpressure. Try a header pipe and you should get about 7800rpm.

THE G-38 IS A FINE ENGINE FOR WHAT IT IS. BOLD MUFFLER MAKES A PITTS STYLE MUFFLER FOR THE G-38 THAT WILL LET IT BREATH. AN 18X10 MEZJLIK PROP WILL HELP.

Or Bolly 18/10. I was getting 7600 with stock mufflers on a pair of old G38's