Some years ago, I was fooling around with an antique lawn boy with a stuck piston. Wouldn’t budge.
Ended up stacking enough fittings together to adapt the spark plug hole to a grease fitting. Grease gun popped it right loose.
Heck of a mess to clean up, but I was surprised how well it worked.
Hydraulic pressure is a good way to move something, but how many grease cartridges did it take?
You were probably lucky that the valves were closed. Wouldn't work if the engine was stuck on either an intake or exhaust stroke.
