[Christ]

Piston speed isn't necessarily determined by engine speed, and the piston can fall away from the expansion of gasses at MUCH lower speeds than 6500 RPM. It's also dependent on stroke length.

For example, in an engine with a stoke of 35mm, piston dwell time is going to be much higher than in an engine with a 20mm stroke. A shorter rod will accentuate dwell time and acceleration, as well as offset angles more steeply. Longer rods allow for a closer-to-straight-line xfer of power to the crankshaft. Longer stroked engines, with higher dwell time (at TDC and BDC) also have higher acceleration and mean piston speeds, during up and down travel.

Remember, higher dwell time means that the piston has less overall time to complete the up or down motion in the same 360* for the same engine speed.