I got a puch Newport from a neighbor. It needed a carb clean and fuel filter and then it was up and running. After a while of riding I tried to start it one day and with the clutch in the pedals would not budge. So I took off the flywheel cover and the flywheel was stuck. I am able to turn the flywheel with a socket wrench to free it. It stays free for the ride. Then after cooling down it gets stuck again. No weird noises. I sprayed wd40 in and cleaned the top of the piston because there was a decent amount of carbon build up but there were only slight scratches. The piston is completely freed up with one turn of the socket wrench. Any ideas??