I am looking for some assistance with a ryobi prob I am having. I have the conversion completed, and the engine running but... the problem I am having is a pulsation at WOT. It wont transition from idle to wide open cleanly unless it is fairly slow and it pulses at the top of the range. I can get it to run cleanly then the next transition, it starts pulsing again. I tore it down and re did the gaskets on the backplate (suspect) and carb base but not the carb itself. My thoughts were an air leak as turning the needles over 3/4 of a turn didnt effect the performance. Today after the rebuild the needles were making a difference, but it would pulsate. On a clean transition, it would turn a 18 x 8 @ 7900rpm. The carb that is on it now is a Walbro (dont have the # in front of me) but is bigger then what originally came on the engine. Any suggestions?

Thanks,
Warren