I'm going to assume you have a Chinese 2 stroke engine with a manual clutch. I'm not certain from your description but it sounds as if the engine isn't turning over when you release the clutch. That can mean you have a clutch adjustment issue.
What "pin" are you talking about? In the center of the engine drive sprocket is a steel pin, about 5/16", or 8mm in diameter. It pushes against a ball bearing and in turn disengages the clutch. It MUST be there as well as the ball bearing. Both should be lubricated with bearing grease.
I'm still not clear on your problem. Does the engine start and run, or does it not run at all? There are many other things to look at if the engine isn't starting, so try to be specific on what is happening, or not happening.
If the chain locked up in the clutch actuator cover it is probably too loose. You'll want 1/2" to 3/4" of slack in the chain. Too loose and it will bind up on the drive sprocket.
Tom