got a different carb on today with an adjustable high and low needle, but the engine only made 6000rpm with a 15x10 prop.. does it need a new ring, or is that rpm about right for a stihl 30cc engine? it seems to be a little weak to me, where is a good place to get a ring for this engine for a decent price?

also the engine wasn't real reliable, it would run great on the table and then i would get it down on the runway and it would die half the time, the other half it wouldn't make full rpm, but every once in a while it would run up strong, it would fly slow, barely enough power to fly and run fine the entire flight and landing and then taxi back, then i would kill it, put it on the table, top off the tank and fire it up again only to find it not running right!! i spent about 5 hours working with this engine all day today, and it only was dependable about 3 or 4 times, the rest of the time i was working on it! i spent a very frustrated afternoon, could low compression cause this unreliability? the engine has to have some compression to turn the 15x10 6200 rpms and the 16x6-10 6000rpms, but this is barely enough power to pull this plane, i would be fine with that, what i am not fine with is the unreliability of the engine!!! any suggestions?