my little farmall cub [ '49] gave up on me yesterday while mowing, got fuel, when it shuts down it will imeadatly restart and idle fine, when i engauge the mower and the tractor starts moving it will run from 1 to 5 or so minutes,terraine is level semi smooth, [ clumpy grass] it has been raining, im thinking moisture in the kill switch,even though the tractor had a tarp on it , thinking that, as i just had the hood off to fix the exhaust and took a look in the gas tank while i was at it, all looked well, i had the problem last year once our summer rains started, but... can that be the problem, or am i dealing with a fuel problem, i have good flow, the mixture is set for the fastest idle, enritching it slightly slows the engine down