Engine RPMs on bikes and cars differ greatly. Why ?

Curious, does your post have no body text?

For the most part it’s a matter of scale. A bigger displacement engine has more recipiocating mass putting practical limits on RPM. While a bigger engine can be built for high RPM the vibration and noise is a distinct drawback in a car but not as big an issue in MCs. Engine designers can trade low RPM torque for high RPM peak horsepower as appropriate.

The OP is missing, a problem I’ve seen a few times in the last few days. I’ll close this thread and suggest that xash try again.