Only sometimes. Always when it's least convenient. I've checked all the safety interlock switches (seat is bypassed by the previous owner, so just the arms and blade switch) and all are testing fine. Battery is fully charged.
When I turn the key, I hear the click as it powers up. I can hear the click of the relay if I move any of the interlocks, so that seems to be working. If I turn the key further to engage the starter, I can hear the starter solenoid (I think) engage solidly (it disengages if I break any of the interlocks), but it doesn't spin the starter. Sometimes it will eventually decide to spin the starter after an arbitrary time period. Other times it'll spin immediately (like you'd expect) and the rest of the time, it does nothing at all.
I plan to test the current draw when the starter is 'engaged' but refuses to spin, in hopes that this will tell me if it's a starter motor issue, or somewhere else.
I figure it could be a dodgy connection between the starter solenoid and motor, or maybe brush dust/grass/dirt accumulated in the starter motor itself. This is a well used machine - somewhere over 3k hours (the meter stopped working) so anything is possible. I have the Kawasaki motor.
Any suggestions on where to start looking to chase this down? It runs and mows great when it decides to start!
Catch it when the starter does not want to spin, have someone turn the key as if to crank the engine. Tap the starter with a hammer and see if it breaks loose and turns the engine. If this does happen, replace the starter.
NEVER strike a starter with anything to is if it works. Internal magnets are very brittle. I suggest you take a battery voltage reading when the ket is in the start position. Dropping below 10VDC indicates a bad battery. If above I would be checking ALL connections between the battery, solenoid and key switch. Let us knew what you find.