Wheel Horse electrical systems were very simple, but after years of neglect and abuse inevitably become unreliable and difficult to troubleshoot.
Ignition switches, seat and PTO interlocks are the usual culprits causing either the starter solenoid to be disabled or the power to the coil to be removed.
Sticking solenoids and failing starters make starting difficult and painful. Unfortunately for many a hammer or screwdriver seems to fix them, but leave them in a sorry state!
Here is an engine cowl which has clearly had a sticking starter bendix...
and one that has been treat more tenderly...