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.