I'm doing some work on a 1981 Puch Maxi for a friend. Everything was going fine untill i came to the engine rebuild. I dont know what the specs are for the engine, or the lubricants it uses. I spotted what looks like a drain plug in the bottom of the casting fot the transmission. Does oil go in there? If so what kind? If anyone knows the gap for the pints it would be very helpful. Thanks