I recently converted a weedeater Ryobi 33cc to an airplane engine. The conversion went smoothly and it started and ran (past tense) like a charm. After about one hour of accumulated time on the test bench (32:1 break-in mixture) it now will only run at half choke at full throttle!! It dies at no choke but I can throttle it down. When I go from half choke to no choke, it revs up to about 6,200 RPM (on a 18x10 Zinger) and then dies out. This model Ryobi has only one needle valve for the high speed mixture. I have adjusted it to no end and still get the same die off.
I'm pretty sure it is a fuel problem but I'm afraid to tear into the Walbro carb. Any suggestions?