Yamaha Big Bear Backfiring

[Jimford]

My Girlfriends father has a 2000 Big Bear. When you ride full throttle for more than a minute it will start backfiring and running like s#!t. I think maybe the needle might be set a bit lean but I don't know. Anyone know what might be wrong with that piece of non honda crap!

[Pappy]

its quite possibly a lean condition. if its not hard to get to try a carb setting change to see if it helps. my eiger 400 will backfire slightly if i run at WOT for an extended time but not severly. i havent changed a thing because i beleive the timing set up on the engine is primarly set up for low to mid range and the backfire is caused from an overrich condition when i let off the gas after a high rpm run. but i aint no expert....so maybe do a high speed plug check.