MOPED ARMY

That's from a scooter . Check the rear near the axle for a model number - If it's a GY6 it's variated If its starts with QMBxxxxx then its a sealed single speed 2-stroke . Since you stated it's a 4-stroke - It probably is a 50cc GY6 .they also made a 150cc version . Most if not all GY6 engine /trans are the same and interchangeable . Look here for answers grasshopper http://chinesescoots.forumwise.com/forum.html