Is that a Kohler 12 hp?...
could be the coil but recheck the points ... the may be just a little off... also did you change the condenser along with the points?
The coil is an easy checkout .. IF its the engine, with the big external automotive coil that I am thinking that was on that ... BTW that's a good old tractor... have not seen them around in many years.. :smile:KennyV