pto this is just a shot in the dark but i have a 18.5 B&S on a Craftsman LT 1000 and messed with the problem of mowing for 1/2 hour and it would shut down, then restart mow for 10 min same thing..... never failed to start and run strong for a while. This came on slowly . Turned out to be a fuel cutoff solonoid was getting weak while it ran or maybe heat. but it would act ok if you just turned the key on it clicked like it was working. So just as a test , I unscrewed it from the bottom of the bowl,disabled the little plunger(read, broke it off!) off the fuel solenoid , screwed it back in, taped the wire back and its been fine since the last 1/2 of last season and all this season, just have not spent the $45 for a new solenoid. Like i say this may be totallyoff base but I know how aggravated I was with it