Looking for suggestions as to why I can't get my idle speed down below 1500 rpms. I have a P12 with a newly rebuilt 230 and a George Asche rebuilt carb. Runs great except for the fast idle. The idle adjustment screw is backed all the way off, the throttle linkage return spring is in place and in good condition, and the throttle arm on the carb appears to be all the way back at rest. The timing is about 6' advanced. I could not find any vacuum leaks using both carb cleaner and unlit propane at th