Just antoher FNG!!

Just got 2000 Foreman S yesterday. Got it from a auction for $2300. It was a theft recovery. The battery was shot and the cover that goes over the display and headlight is gone. Tires almost new. Had schelacy (not spelled right im sure) stuff from the old gas in the tank. Started right up though after new gas. Stalled a couple times, but pretty sure carb was gummed with the schelac like gas. Once I cleaned it up havent had a problem yet. The only thing is reverse. I am not doing something right or its out. Cant find anything except on the display the R that thats next to N. Tried Shifting down past neutral, the N light goes out but no reverse. There is no owners manual and dont know to much about it. THX for any help.