$50,

I owned the same engine and same plane. I ran a Xoar laminated 23x8 on mine. 6700rpms... very strong motor...

As to your original question...

Make sure the gasket between the cylinder and case is not leaking (and sucking in air). My engine had this gasket replaced 3 times... it's a problem area for the engine..

My engine would start easy, and run fine, until about 10 minutes into the flight... and bam.. she would just shut down... I changed everything, fuel, plug, fuel line, tank, etc.... I even baffled the cowling.... that help some... but the engine would still just shut off...

I replaced the gasket and it fixed the problem... but the replacement gasket from Horizon would fail after a few flights... It's really a same, because the engine was smooth... and a big time power house...