How to install a bigger crankshaft

[gitsum]

Originally Posted by blueboy5000

I cannot agree that it is a good idea to run at WOT or close to it, especially uphills or in hot conditions. My bike also hits 60 around 6500 rpms, but at WOT is is pushing 10,000 rpms, I would NEVER ride at approaching 10,000 rpms.

Is that 10,000 rpm's during acceleration or top end? If the engine runs that fast during WOT acceleration, then your variator weights are too light. If it hits 10,000 rpm's at top end then your gearing is too low.

Optimum gearing is reaching the maximum horsepower peak at top end speed on level ground.

You can change this with higher gears in the transmission, heavier variator weights, a larger diameter rear tire, shortening the variator boss, or any combination thereof. Just like tuning a carb there are multiple parameters and it can take some trial and error to get it right.

WOT itself is not always a bad thing, it is the combination of excess heat and too high rpms that you want to avoid. Some motorcycles/scooters are tuned/geared so that wide open throttle causes both, some are not. The GY6 engine is susceptible to higher engine temps when running a little lean, kinda of like a two-stroke, but not as much.

Proper carb tuning and optimum gearing can allow a GY6 scooter to perform at a higher level without compromising engine longevity/reliability.