HEY homerj, fancy meetin you here
hehe. To change the piston, take your velocity adjuster screw/knob out, remove the spring pack, then pull out the old piston. Then drop the new piston in, and "press" it in with a rotating, round and round motion. That helps (at least in my mind) keep the oring from being sliced. By the way, wait till we show you Shanes Mini/BooYaaH/LVL10!!!!! Your gonna LOVE this!!Later.