Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Can you tell me which model, spec, and serial Kohler 12hp you have please?
This is the point and condensor system on your engine, correct?
If you are getting 12v to the spark plug wire at all times, then you have a shorted secondary winding within the coil. You should have 12v going through the primary circuit (small connectors on either side of the coil), and then when the field is collapsed by the opening of the breaker, high voltage is induced through the high tension lead to bridge the spark plug gap.