yes, Zenoah engines are piston ported, most chain saw engines are of the piston ported design, engines like Desert Aircraft, DL, 3W, are all reed valve engines, at the rear of the case there is a reed valve that opens and closes with engine case pulses to allow the fuel to enter the case, then be drawn up into the ports to the cylinder, on a piston ported engine, the fuel enters the cylinder from the carburator as the piston moves down it pulls fuel into the engine from the cylinder and then it flows down into the bottom of the case to be drawn up the ports to the top of the cylinder. I hope this makes sense to you.