Well, let's see what happened today.

1. Ran the motor again with the 20x6, about the same results as yesterday, though today is a little warmer.
2. Took the muffler off, no noticeable RPM gain.
3. Put the muffler back on, same results.
4.Put on a 20x8 prop, got 5800- 5900 RPM but felt a lot more thrust standing behind the test stand.
5.Played with the idle, anything below 1800 and it started shaking quite a bit.

I kind of like the 20x8 prop. Any ideas on what the safe high-end RPM is for this engine? Personally, I'd rather lug it down a little bit than over-rev it.

PS: after a couple of hours and a couple hundred expletives, I got a spring back into the carb barrel on the 34cc carb,so now it has the tension for the barrel but not on the throttle arm.

J