Dirt Atv Track Cakes ATV Backfiring?......?

ATV Backfiring?......? - dirt atv track cakes

I have a 2002 Yamaha Warrior 350 ATV. I kept myself in good shape because there are no deep scratches or dents on the body. Even if I rode one day with my friend and I were more difficult than usual. It was a dirt road and roads were very different.
A few days later I was with him, I took my bike for a short walk, and I noticed that he cons-productive time to time. There is a strong opposi-productive, as it seems to run 2.3, as a rule, when the gas stopped.
I've never experienced with my ATV disadvantages productive for the day when I went with my friend. What is the origin of evil? Is it difficult to repair?