Hey, I just picked up a 2007 Yfz 450 right off the show room floor. It has a K & N air filter on it and the exhaust is super hot. Is this normal? I heard that the Yfz's were known to run to lean off the floor, and with the filter and allowing more air in, I guess it's running even leaner?

 

Yep, the air filter will make it run more lean, the YFZ450's exhaust are hot anyway. It may be a good idea to do a jet pass and if the results show a too lean condition, jet it a little richer. My buddy always complained about how hot his was, it was always burning through his pants leg. I measured his exhaust pipe where your leg rides with my laser thermometer at over 700 degrees, and as far as I know it was jetted properly! For comparison I measured the exhaust on my Warrior at 400 degrees.

 

yup all my riding jeans have holes on the inside knee area. Burns right through them.