Motorcycle Repair: 2002 vl 1500, air fuel mixture, air leaks

Question
been having trouble  with backfiring through carb

Answer
Dude,

Lean carburetor settings can contribute to carb backfiring. If the mixture is too lean, it may burn very slowly and unevenly. This condition, in turn, may result in burning mixture remaining in the cylinder until the beginning of the next intake stroke when it can ignite the incoming air/fuel mixture.
Air leaks around the carbs can lean the fuel mix.
Check timing and valve clearance.
Make sure bike is rejetted if using
aftermarket or low backpressure exhaust pipes.