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I have owned since new, a 2002 M-48 Tank Commercial 19hp Kawasaki, about 1200+ hrs. Recently, upon turning the key to start the engine does not crank over. The inline fuse is blown, this is located on the wire from the + battery side of the starter solenoid within the wire loom. I have replaced the solenoid and key switch just to eliminated some traditional problems and because I had them on the shelf. IF I turn the ignition "ON" and jump the terminals on the solenoid the will engine start and tractor operates perfectly, even with blown fuse. All the wiring is in decent shape, have checked connections and nothing broken or damaged. Tractor gets parked inside, and not one to wash as the picture shows a good layer of dirt, so even though 20yrs old not a lot of corrosion. No mice have chewed wires. Cannot figure out why fuse keeps blowing when key is turned. But engine will start when solenoid terminals are jumped. Would the starter be the culprit and be pulling too many amps or shorting out???

My WAG is a chafed wire in the safety interlock circuit.

Yes, i was also thinking a safety switch is causing the short. Next step is a continuity test on each switch.