Chris Maybe you got lucky and your stock crank bushing did not fail but I saw a few that did fail at hi rpm. I toasted one my self running 17x45 gears in a few days. I run 17x36,17x38 and 17x40 on my e50s. With a tuned 2 shoe with thick springs and estoril pipe My bikes take off as fast as my wife's mini van and go 55+ mph
2 stroke has nothing to do with rpm 4 strokes rev also.
It's all in your tuning preference. If you take a stock 2hp e50 that rated at 2 hp@5,000 rpm and 2.06 ft pounds of torque @4500 rpm and spin it at 11,000+ with triple or quadruple the hp and torque a stock crank will fail so I have found
if you keep the revs down the crank will live even with hi hp & torque. It's the same
for kits they all have hp.torque and rpm specifications if you match them with the proper pipe and gears you will have good combo. If you port your kit, get a hi rpm
pipe and lower gears for hi rpm ect, you are changing the specs so you need to engineer and blueprint your combo. Not just bolt on and go. Rebuild with a needle bearing crank, new bearings, coat drill cooling holes in piston ect, Should be used for hi rpm combos. I don't have nothing against hi rpm screamers each to his own I got
a few hi rpm pipes and engines I could bolt on when ever I want to so don't get me wrong just for someone new to kits and hop ups to mopeds I say low rpm hi torque
is the way to go