The primary cause of severe kick-back, where the engine fires and even backwards and catches the pawls of the crank, tuning it into a death machine out of a Kung-Fu flick, is that the spark is occuring before TDC.This is a big reason why it is relatively safe to crank a tractor with a conventional Kettering system that is also equipped with centrifugal advance, such as other Farmalls and many John Deers. If functioning properly, the centrifugal advance usually assures the spark is retarded past TDC for starting. On Model T, where the spark advance was manually set by a lever on the steering column, many a child and other non-driver was taught to get "get that spark lever down!" on command once the engine fired. That way the person cranking could start with the spark well retarded, which often made the engine splutter and miss and only run for few critcal seconds but which assured SAFE cranking. (And, there were even a few ancient cars, like some Packards, where once the engine is warmed up one has only to flick the spark control through its range to start the engine WITHOUT cranking!) So, check the mag for correct operation. In the meantime, be VERY careful cranking this tractor! Henry Leland, head man at Cadillac, commissioned the first modern self-starting system from Charles Kettering, because a close friend of Leland's was killed cranking a Cadillac. Never wrap your thumb around a crank. (Or a steering wheel when going cross-rows!) Always pull UP on the crank, standing slightly off to the side. And, as others have said, ALWAYS have the spark retarded below top dead center!
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