I have a 78 Puch Maxi. When I ride it even now and the the engine will stop and lock up or seize up. The bike slows down tremendously and comes to a stop. I try and pull the clutch and restart it but the fly wheel won't spin free until a couple tries at it. Im unsure if its my transmission fluid getting clogged up or not. Please let me know if this explanation helps enough and what I could try, thanks.