I have a B&S ( 14.5 HP ) engine which had a carb rebuild last year and ran great. The tractor sat outside over the winter. And so far I have cut the lawn 3 times this year without a problem. Yesterday the engine just started to sputter ( after I ran it for say 30 minutes ) then died. I waited about 1 hour and was able to restart it and drive it to a location where I store it, then it died again. This morning I started it and it ran again for a few minutes, then it died again. I have drained all of the fuel out even though there was brand new fuel to begin with, and put new fuel in ( 1/2 gallon). But it won't start maybe because not enough wait time has elapsed. But if it does start again and runs for only a few minutes, then cuts out, what could be the problem?