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The Home Smithy
The Home Smithy, Small Engine Tech
Category: Small Engine
Satisfied Customers: 9622
Experience:  Small engine tech
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Ignition problem on JD 110 Lawn tractor 1971 Kohler engine

Customer Question

Ignition problem on JD 110 Lawn tractor 1971 Kohler engine with Magneto alternator under flywheel. I replaced a fried ignition coil and suspect the stator is bad. Have also replaced spark plug, points, condenser and spark plug cable. The starter will crank if white wire to condenser and points is disconnected. When this wire is connected the ampmeter needle pegs to negative like a short and will not crank. What could be the problem?
Submitted: 8 years ago.
Category: Small Engine
Expert:  The Home Smithy replied 8 years ago.

Hi Customer;

Where does the other end of the wire conect to? The ignition switch? Or the coil?

Customer: replied 8 years ago.
It connects to the ignition switch.
Customer: replied 8 years ago.
Additional info - This is a Magneto flywheel type ignition with 10 Amp alternator with a permanent magnet ring on the inside of the flywheel which revolves around the stator and coil as referred to in section 8 electrical systems and components (KOHLER ENGINES SERVICE MANUAL - K -SERIES K91,K141,K161,k181,K241 etc. The Manual does not show a wiring diagram for this particular ignition system.
Expert:  The Home Smithy replied 8 years ago.

Ok the wire to the points and condenser should come from the coil not the ignition switch. The wire from the ignition switch goes to the other terminal of the coil.

Basicly when you plug the wire from the ignition switch into the points you are causing a direct short to ground.


Best regards, XXXXX XXXXX Smithy

Customer: replied 8 years ago.

Smitty ~ Why has this engine run for 37 years with the wire connected from the switch to the condenser? One of the coil wires under the flywheel runs to the condenser terminal with the wire from the switch and jumpers from there to the points by a 'y' connector. The other coil wire is connected to ground on the stator which is attached to the engine and is stationary and a ground.

Expert:  The Home Smithy replied 8 years ago.

Ah ok you have a bassakward ignition system. It uses the positive for a ground and the ground for the positive. Many older diesel trucks used this type of stystem. I almost smoked a guys whole electrical system once due to this set up.

Check that you have the battery set up the same way. You may have installed the wires like a normal automotive set up. This would again cause a direct short to ground.


Best regards, XXXXX XXXXX Smithy

Customer: replied 8 years ago.

Smithy ~ The battery connection is and has always been Negative to Ground. I also ran into your same situation on an old International truck and blew up a battery when trying to jumper with cables. Whew!!! I don't feel you have answered my question or helped me solve my problem. There has to be a short in the stator winding? or something else. I didn't want to take it to John Deere and pay $500 bucks or more to get it fixed.

Expert:  The Home Smithy replied 8 years ago.

Ok You say that the wire going to the points comes directly from the positive wire of the battery (through the ignition switch) without going through the coil. And that the negitive side of the battery goes to ground.

Please look at the following diagram of a 12 volt ignition system and tell me how that can work, please.

I must be missing something here.