Re: no max rpm?
While a maximum RPM is not usually stated for outboard 2 cycle engines, they are Usually rated to run in the range of 4,500-5,500 RPM, and some as high as 6,000. One of the reasons for this is that above 6000 RPM, the efficiency and responsiveness of the reed valves decreases and horsepower will in all likelyhood decrease. HOWEVER, reeds themseves can be run to at least 20,000 without damage as demonstrated on some model airplane engines. Granted, they are smaller reeds but still-- Also, consider that the reeds on woodwind instruments, clarinet, sax, oboe, etc, will approach say, 10,000 cycles per second on a very high note and that doesn't tear apart the reeds too quickly. (normal human hearing--20-20,000CPS).
The engines, having usually a very short stroke and no reciprocating valve train to float are in my opinion, good to at least 10,000 RPM or until the flywheel explodes. I have never tested an engine to this point and probably never will though. An argument could be made that some dragsters regularly run over 10.000 RPM and while a flywheel explosion protector is required, a grenading flywheel is relatively rare.
