Hello Robert t, Check the simple things first.
When the unit won't start does it have battery voltage at the coil???

I think your coil might be heating up or the condenser in the distributer and breaking down
(I assume it has points for ignition)
Could be lots of fun stuff. Is the unit GAS or Propane powered?
I have seen crazy little gremlins that can cause you lots of trouble.
One step at a time, let us know