Just from personal experience with mine- if you can remove the airbox lid. You have an aftermarket fuel screwi have a 2004 yfz, its running way to rich there is currently a 172 main in there with a 42 pilot, im running a biggun slip on with the air box lid on but with vents instaled. i am getting a lot of back firing and when the throttle is tapped and let out it is throwing a flame about 8 inches. im at 853ft above sea level. what should i change my jetting to?