50 cc Beamer ll with erratic idle

The reed valves should be closed at rest. When the piston creates a vacuum in the crankcase, the vacuum will open the reed vavles to allow fuel and air in. When the piston is traveling back down and creating pressure inthe crankcase, the reed vavles will close. They work kinda like a check valve. With a reed valve broken off there is nothing to stop pressure from moving either way, so when the piston moves down it forces air all the way up to the carb instead of pressurizing the crankcase. It seems reasonable to me that if vacuum can draw fuel from the carb into the engine, positive crankcase pressure could force some fuel out where it shouldn't come out. That's why I suspoected the reeds, but it's best to do the quick checks for vacuum leaks and things like that before disassembling a lot of stuff.

The piece of reed valve that is missing is not as big as the one in the link but bigger than the small pieces shown. I pulled the head and removed the cylinder and they both look okay. I'm hoping that the piece of reed valve that is missing passed through the engine on the initial loss of compression. I'll keep you posted.