probably the same answer but i'm feeling helpful so here goes.

turn the crank cw untill the piston just closes the exhaust port, feed through the plug hole as much braided nylon rope as possible and tighten the hub, back off on the crank and rope comes right out. this is the safest and easiest way to lock a piston on any engine when you need to apply alot of torque to the crank.

dave