How do you pull drive sprocket from engine

mine tends to just fall off

you need to turn the center screw of the puller while holding the puller with a crescent wrench to keep the outer part of the puller from turning. Its a 2 handed job.
be sure to screw the puller on all the way the insert the center screw into the puller tightening up the center screw forces the sprocket or gear off of the shaft. be sure clean the threads and lube the threads with oil or anti seize to prevent the threads from galling.
hope this will help you to get it to working if not re read the threads on engine tear down I show a almost step by step how to on removing the front engine gear, the puller works on all of the gears and sprocket on these engines.