I have a kohler 25 hp on a simplicity tractor. Turn the key nothing but I can jump across starter the engine starts then shuts itself off in about twenty seconds.new starter and switch

Need a meter to start checking what's causing short switch solenoid broken wire grounded wire safety switch fail starter failure

The keys are not dropping in the clutch fan. Lightly tap with hammer before attempting to start. Will need to replace eventually.

try jumping the battery with your car battery first. if it cranks, charge battery and possibly adjust valves. If not, try jumping directly to the starter. If that works, replace the starter solenoid. If not, might be the starter itself.

check fuel filter, it may be clogged, if so replace

I dont have all your anwers. In my experience, Kohler frequently has wires to start, run and stop the engine. They also frequently have a low oil and/or high heat control (engine shut down). Also expect a wire from the charging system. On your tractor, you probably have similar plus 'operator presence' wires. These wires require to you to be sitting in the seat for the machine to operate - a seat switch for example. On my tractor, I can depress the 'brake' (which isnt exactly a brake in fact) and the engine will run when I dismount. However, if the mower is engaged, no matter what, if I get off the tractor, the engine shuts down.

You will have to determine what every wire is for and connect it properly. You may lose some engine 'functionality' or tractor safety features. It is never easy to put a Ford starter on a Chevy. Good luck with your project.

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sounds like the starter drive is worn out or the drive gear is not engaging the flywheel need to remove the starter and check drive gear

Could be, but test each item with your tester. Test key switch (12V in and 12 V out when turned to start., operator present switch 12V in 12V out (seat) Clutch switch, etc. till finally you test for 12V on the small terminal on the starter solonoid. Happy testing!

Sounds more like a safety switch problem, first verify the seat switch then the mower switcher and make sure it's not in reverse.

sounds as if you have one of the safety switches keeping the starter from cycling. If it cranks over when you jumper across the starter solenoid then it is a safety switch. they are usually under the seat, on the clutch pedal, on the blade engagement lever and on the gear shift which has to be in neutral

check for voltage at starter whe turning key to start if you have 10 or more volts the starter is bad if you have around 4 volts try tapping on starter while in the start position on key may just be froze up.if you have no voltage at starter then the solenoid may be bad.