ORIGINAL: fastpat
I read an evaluation of this engine, and one of the two evaulators recommended not disassembling the engine for reasons he couldn't explain or didn't know. Curious. I reckon I'll find out about this, on one engine at least.
According to O.S. the engine weighs 11.8 OZ and puts out 1.27 hp at a screaming 17,000 rpm. The weight is probably without what passes for a muffler.
http://www.osengines.com/engines/osmg1400.html So, in comparison with most .40-.45 engines, it's in the ball park for power to weight ratio.
I've seen a few review pics of them disassembled and there isn't much in there by comparison to Mazda wankels. There appears to be some needle bearings that support the rotor and perhaps the eccentric shaft (crank). The rotor has three apex seals, presumably with wave springs underneath as per most wankels, BUT it has no obvious side seals. The lack of side seals suggests a closely toleranced engine OR one that depends a lot on the fuel/oil sealing. In other words be careful if tightening those through bolts or you may destroy the tolerance or the rotor sides itself.
While OS make good engines I've always been doubtful of their max rpm stats. For example, a 40LA is supposed to do 16000 rpm but the best I could ever manage (with realistic prop sizes) is 13000. Also consider that OS quote the same max rpm for both a 40LA and a 46AX, which are wildly different application engines. Once again, my AX does 14300 rpm with a 11x5 prop and not the 16000 claimed. My guess is the wankel will probably peak out around 14000 rpm with a reasonable prop and nitro content.