I've had this engine since new, never been crashed.. The problem seemed to slowly occure. It will start fine will idle and accelerate ok just a little slow on acceleration. The low end addjustment is working, it will change the idle. The high end will change the RPM at full throttle but where it runs best is 1/4 turn out. I thought it use to be about 1 turn. Running an OS-F plug 10% wildcat fuel 14/8 prop. Any ideas?

Over time, vibration can cause the needle valve to damage the seat in the carburetor body. One way to check is to remove the high-speed needle and look at the pointy part. If you see a polished ring around the pointy part, it's likely it has struck the needle seat at some time. We've also seen this happen if the needle has been tightened instead of gently closed. The "cure" is a new carburetor body and needle. All the other parts can be reused.

Bax is right on. It took about three years of pylon racing with 40% nitro to wear my needle out. A new needle cured it.