quick question. i just bought a 350x out of a ladys barn. was a little rough but new the ladys nephew and he said that his late uncle took good care of it an maintained it well. anyways got it cleaned up cleaned carb and fired right up. my prob is it runs great with choke on once i turn off choke it runs good at open throttle, but once i let off it wants to back fire and wont idle. i was running 2yr old gas so in process of draining tank and gonna throw new plug in today. this may be the culprit. any sugestions otherwise. this is my 1st 350x and i gotta say i love this thing ive only ever owned tri-z's and never thought i would shy away from 2-strokers but this thing is fun.