My old motor died so I got a used 17hp Briggs and put it on my tractor, I got it wired and it fired right up but after running for a few mins. it started blowing out white smoke and died, it started back up but then started blowing smoke again........what should I check on the motor? It was dark out when I got it running and pulled it into the backyard so I haven't had a chance to get a good look at the motor to see if there is anything visable as to why it started smoking, I just parked it and came in. I did have to swap out the carb from my old 13hp motor because the one on the 17hp motor was flooding out the engine. The motor in it now is a Briggs 310707 0137 E1....I did get the motor for free from someone that said it was good, it had been sitting for a long time and not ran. Any help would be appreciated.