backfire

Recently got a 1990 Superjet and the bendix was bad. Bought a new bendix, installed it, and put everything back together. Now the engine won’t fire up and constantly backfires with a loud pop every time I try to start it. Any ideas?

Hey everyone I just got a superjet 650 that's bone stock for now. The ski looks great and ran great the first 2 times I took it out, but last weekend while I was riding it seemed to start hitting the rev limiter out of no where. I was on a lake so it's not like I was surf riding and hitting the...