Never had a problem with my 08 rancher 420 until now. Rode last week and it ran for about 10 minutes then started sputtering as if i just kept repeatedly punching the throttle even though I was holding it steady. Didn't have enough power to go up a small hill. Took it home and changed out the spark plug and put some gas cleaner in it to clean out any dirt or whatever might be in the gas. Rode it for about 30 minutes and it ran fine, met up with some friends and had it idiling for a few minutes then as we started to driving off and it started doing it again except worse and it wouldn't stay cranked. I can let it sit for awhile and it will crank up fine but after a few minutes the problem starts again. What do I need to do?????? I want to ride tomorrow!