2008 Polaris ATV Sportsman 300 400 H.O. Service Manual, Page 203Get this manual
ELECTRICAL Ignition System Testing
Whenever troubleshooting an electrical problem, begin by checking all terminal connections to be sure they are clean and tightAlso be sure that colors match when wires are connectedUse the following as guide for troubleshootingCondition: No spark or intermittent sparkVerify 12 Volt DC power is present on the Red wire entering the CDI BoxReplace Spark PlugRemove or isolate the BLACK wire from the 3-wire CDI box connector to isolate the ignition system from the ignition STOP circuitsBe sure the CDI box has good ground connection on the BROWN wire at the 3-wire CDI box connectorDoes it have spark? No Verify that minimum of 10.5 VDC is getting to the CDI box during crankingTest the stator Pulser CoilRefer to "Cranking Output Tests" and "Resistance Tests"Are all tests within specifications?
-Test the key switch, OffRun switch, and ETC circuit for shorts to groundYesCheck connectors for moisture, wire color matching or corrosion