Not worth the trouble IMO. Had one on a ST3000. Hated it. Wouldn't deliver enough fuel to satisfy the engine.

You might look at the Perry 30 pump. It requires a tap into the backplate and works off pressure pulses. Problem with that is that all 4-strokes have a crankcase vent. You probably won't get enough of a pressure pulse out of the engine to work the pump with that vent tube open-- as it should be.

I don't think you can just use the crank vent to run your pump. I'd imagine that the crankcase needs to vent to prevent pressures from building up inside.