Bike: 2000 Yamaha yz426f Stock exhaust, stock air filter. I took it on its maiden voyage Saturday after plating and I know it kinda sputters at cruise/part throttle sometimes. Didn't think much of it but when I was on my way home from this short ride, it came to a sputtering/backfiring stop like it ran out of gas. I was riding up an incline and it had plenty of fuel in it. I tried numerous times to try and kick start it again after the incident and it would randomly start for like 5 seconds then backfire and then die and not start again. Towed it home and now it starts up just fine on the stand. Maybe I'm to short but I leaned it up against a crosswalk light and it still wouldn't start. (I don't normally have to do this but I thought that maybe I wasn't kicking hard enough) Maybe a carb cleaning and new gas? This gas has been in it since winter. It idles fine, but I know when I try to go from a little bit of throttle to WOT or close to it would hesitate then kind of sputter then kick in like vtec or something. What do you guys think?