How many hours on the unit ? The experts need the full model and spec letter to know which gen you have. Yes the piston can get stuck on a ridge at top.
The valves can be to tight. Loose connections , battery , many things to look at.
The reason I ask the hours is because a friend of mine had a 4 ky locked up it had about 1800 hrs on it. This one had formed a ridge at the top of the cylinder so the piston was stuck on it. Hit it with a wood block and hammer and it popped loose. The gen had been run low on oil so we called it doa and not put any money in it.
