Originally Posted by Ludford
I took of the cylinder head and gobbed oil in there, rocked it back and forth and the engine unsiezed. There's no cylinder wall damage.
However after spinning freely for a while the engine will seize again and has to be rocked back and forth to unsieze.
Oh really? wow, I'm sorry, I'm not an expert on these engines. It's possible that the piston rings are not lined up properly. I would try pulling the cylinder off and checking the piston rings. There should be 2. Make sure they are each in their grooves on the piston. Slowly rotate each one until they won't spin anymore (are stopped by a small piece of metal on the piston). Make sure that you can squeeze them together with your fingers against the piston. Now try to put the cylinder back over the piston. Squeeze the top ring with your fingers and slowly slide the cylinder down over it, do the same with the second one then slide the piston down against the gasket on the engine case. Now try to engage the clutch and see if it still gets stuck. If it still gets stuck it's possible that something fell into the engine case. Try taking the cylinder off and turning the engine upside down and shaking it, maybe something fell in there.