Along with your MSD, you should have a small diode and instructions for installing it in the circuit. Fan motors etc have enough reverse-current flowing to trigger the MSD indefinitely. It gets boring to kill the engine by letting out the clutch with the brakes locked. And did you add in the adapter so the tach will work? It's extra cost but you do need it. Incidently, MSD has most of these instructions posted on their website.
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