I have run K&N filters without any problems and only had to rejet when used in conjunction with aftermarket exhaust.

 

I have a 00 recon and 04 recon with k&n filter on both ran year round with no trouble I do understand emissions have become stricter but I dont see why it would not still Idle. Neighbor across the street just bought a 450 grizzly same carb he has k&n filter on his seems to run fine in 60 degree or 25 degree weather
Problem I see with them wanting to jet the carb and I still run a stock exhuast when its 80 degrees and riding am I going to burn up the stock exhaust because its getting just that much more fuel. Or case in point when the put the motor back together they have the timing way off and dont want to own up to their mistake

 

Close of this chapter. Dealer called today said Big Bear was ready to pick up they jet both ports. Running good with factory air cleaner, temp is 24 degress runs strong than before. Advised I put k&n back in, in the spring or bring back over and they will reject for summer setting. Called yamaha c.s to ask about what had been done they dont warranty jetting of their carbs,voids warranty if problem brought on by jetting. Here's the confusing part Yamaha admits with clean air restriction at anything under 30 degrees problem may exist, yet they dont support rejetting to make their machines run good. So I am happy B.B runs good starts and idles still have 9 months of warranty left hope I dont have to use any more of it

 

seems to me this is a dealer issue, not the manufacturer. i would take my money elsewhere next time.

 

This could be an issue with the dealer too. I Have had good luck with yamaha in the past covering things. Some times the dealer will tell you they called yamaha but they don't. They would have to admit they made an error if it was their fault.

 

This is a dealer issue and I had the same problem with a dealership and went to Yamaha for the problem to be resolved. They took excellent care of me and the problem and I have complete faith in their product, and their willingness to stand behind it.