ratrod

Yeah I got the engine number but i not sure how to break it down to what numbers mean what.

Hey Iam new here trying to get some help. I built a ratrod bike from parts laying around. I found a motor laying around I do know it is a yamaha 400 but I dont know what year or exact model. How do I figure this out. Any help please so i know what engine to buy parts for. It runs now thank god.