Just purchased a nearly new BME 50 that had previously had around a gallon though it. Im running a 22x8 menz prop on 50:1 Sthil oil. Looking at other posts, I see that people are getting 7000+ RPM on this prop, but mine max's out at around 6400. Initially I thought that it could be overheating, so I removed the cowl (no better). I've checked the system for leaks and can't see any.

Something else thats bothering me, is that the engine doesn't seem to prime itself when choked, but a quick squirt of fuel in the carb and she'll start first flick and draw fuel.

Any suggestions?

Thanks in advance

I am at sea level. I have a few of these (conversions but the same engine) and mine fly best with a 21/8 prop. About 7200 RPM. Tried 22/8 Menz props but could get maybe 6700 or so and being hot and humid here for 8 months a year the RPM will sag. As for priming, check for cracks in the neoprene tube between the case and the carb.

Yeah something is definetly wrong with your bme 50. I am turning a 23 x 8 pt cf prop 6800 rpm. You probably got a air leak somewhere around the carb, hose, or carb block why it wont prime with choke on. When in doubt call bme and see if they can trouble shoot it for you.