I don't know if this is helpful to anyone but, I have a 33cc ryobi conversion running a roy scholl ignition and a wacker engines muffler and a bigger carb. It is on a thunder tiger Giles 202 1.40 size plane.
I had been ruuning a zinger 18x6 prop on it and it would spin it to 7500 Rpm. it has a two ring piston in it which wasa big improvement over the stock single ring, but I don't have any performance records from before I switched it over. It had up till this week a cyinder with the decompression slots. I also bought a Xoar 18x8 prop which I could turn to 6800 Rpm. Taht wasn't too great, it took too long to get the plane off the ground.
So before winter I bought a cylinder without the decompression slots. I bolted it up this weekend and did some tests. the numbers above were done the same day just minutes before I switched the cylinder. with the new cylinder it will swing the zinger 18x6 at 7600 Rpm and the xoar 18x8 prop at 7260 Rpm. I think that should be a lot better. I think the zinger prop is pushing the limits of how high this motor will spin with this carb and exhaust and ignition.


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