My Shee runs like crap. Start up is normal,but after a min. it starts Puffing/Poping out of the left exaust. I happens when I give it 1/4 throttle and then let off, then (puff). The air out of the exaust pipe is weak and no/little smoke.When riding.. if I hold the throttle steddy at let say 3/8 for more than 2 secs. it will "puff" then start to bog down. If I run it hard it seems to do alright. I dont know,.. can someone help me out. Oh ya the bike is completly stock.I know stock, but money is tight.