I am a part time shade tree atv mechanic but I do a little work on the side .  Minor stuff like preventative maintenance like oil changing, brakes, minor electrical I can do ok at but right now I have a 04 honda foreman the owner says back fires pretty often.  I have ridden aroud a little and it has done it 2 or 3 times on me.  its always while decelerating.  I have spoken to several other people who own these and they say they have the same problem.  Is this just a characteristic of this particular machine?  If anyone can help it would be greatly appreciated.  

Hi I just worked on one today, I looked at everything i could think of (valve ajustement, carb cleaning, exhaust header leak ...) I knew it was coming from a lean carb. so I still decided to give her a go, the Quad seamed to get better as it was getting hotter, then I thought of unpluging the carb heater, No more backfiring ????? I'll plug it again tomorrow and re-try it.

Hope it can help you, I'll searching the Net for more info on this problem