98 Polaris 250 trailblazer, idles great, loads up and backfires when given throttle?

Question

I've cleaned the tank and carb, adjusted timing, replaced CDI box. Acts like something electrical. 2 Polaris mechanics looked at it-no go! Any guesses? At whits end!

Answer 1

I have no idea... is it stock exhaust?

Answer 2

these came with a oil injection system from the factory that most people un hook and mix their own gas the problem might be that the pump is still operating injecting air into the system causing the lean issue you are describing  

Answer 3

some atv"S when they get old do that but u might just need to change the exaust