Dont feel alone--- My daughter's troy bilt bronco is doing the same thing. Changed selenoid and it started right off, ran it for a few minutes then nothing at all when the key was turned. Battery checked good(at parts store but it is a small amp (125 or 150 i think,I didint look close). Lights work but nothing at starter. It can be started by jumping off at starter so I expect the safety switches are o.k.. I by-passed seat switch but still nothing. I'm stumped, beginning to think battery because I had one checked at ATV shop for my suzuki and it checked good, started it once and that was it.....
Let me know if you find the holy grail!!
greg