The gentle way to loosen stuck pistons!

[Frank S]

The a fore mentioned methods are tried and proven by many. However the pistons are not the only components which may cause an engine to be frozen in place.
the valve camshafts crank shaft bearings and even the lowly distributor or magneto are a few of the others. on small engines that have an alternator built right into the flywheel the magnets can become dislodged. Some small engines have counter rotating balance shafts which can drop a tooth from their gears. On motorcycle engines particularly those with chain driven overhead cams I've seen them drop chunks off of the chain guides which become lodged in the links of the chain and the sprocket on the crankshaft. These are some of the reasons to check everything before deciding on which procedure would best solve the situation.