Okay so i have a 2006 yz 450. I had some motor work done on it and ever since it has this popping or sputter during part throttle cruising down the road. I was thinking the needle position was way off and i could adjust it to get rid of it. Well i have a wide band oxygen sensor i have installed in the exhaust to read the a/f ratio. At wide open throttle i am right around 13.3 to one and it runs great. However when i am cruising along it was around 13.8-14.0 range and it was sputtering or popping once in a while cruising down the road. I lowered the needle clip one position to raise the needle and richen it up a bit as i thought maybe it was to lean. I think it got worse and was around the 13.5 a/f range. The thing i don't understand is that i have tuned a lot of motors and at part throttle in the cruising range to be at the 13.5 a/f and they ran great and never popped. So to all the dyno guys out there, do the yz450 motors like to run lean? I don't really want to change needles (as i can't lower it any more then it was), and 14:1 is already leaner than i setup most of my other bikes. I don't understand why it would pop and miss at that a/f ratio.