Bought my son a used 2008 outlaw 50 polaris for this christmas. I got it cheap cause engine was smoking. It was extreamly hard to start and would always stall. I rebuilt top end, checked valve clearance and rebuilt. New stator new spark plug..new carb..new throttle cable. Atv starts perfectly runs for 3 mins and shuts off..it will immediately restart and stall..i just ordered a new coil waiting for it to come in. I need this ready by xmas. Is there anything that is known to cause this??