Hydratork Starter, 6mm start shaft with one-way bearing that CLAMPS on the starter output shaft and superb push-in, pull to remove 6mm start extension. This is the solution to those tight engines. (Starter shaft is sold seperately) The Mavrikk HydraTork has TWO strong electric motors ganged up through a super-tough geared reduction unit, motor powered by two 6-cell NiCD packs. Push button switch is easy to reach. (It's a little noisy but it is powerful) (Non-standard oversize output shaft on the HydraTork, but the Mavrikk start shafts and most standard spinner-cup shafts fit in the included spinner cup VERY firmly).