2004 Polaris Sportsman 400 Owners Manual - Page 121

TROUBLESHOOTING Engine Backfires Possible Cause Weak spark from spark plugs Incorrect spark plug gap or heat range Old or non-recommended fuel Incorrectly installed spark plug wires Incorrect ignition timing Mechanical failure Solution Inspect, clean and/or replace spark plugs Set gap to specs or replace plugs Replace with new fuel See your Polaris dealer See your Polaris dealer See your Polaris dealer Engine Runs Irregularly, Stalls or Misfires Possible Weak Spark Cause Fouled or defective spark plugs Worn or defective spark plug wires Incorrect spark plug gap or heat range Loose ignition connections Water present in fuel Low battery voltage Kinked or plugged fuel vent line Incorrect fuel Clogged air filter Reverse speed limiter malfunction Electronic throttle control malfunction Other mechanical failure Solution Inspect, clean and/or replace spark plugs See your Polaris dealer Set gap to specs or replace plugs Check all connections and tighten Replace with new fuel Recharge battery to 12.5 VDC Inspect and replace Replace with recommended fuel Inspect and clean or replace See your Polaris dealer See your Polaris dealer See your Polaris dealer Possible Lean Fuel Mixture Cause Low or contaminated fuel Low octane fuel Clogged fuel filter Incorrect jetting Solution Add or change fuel, clean the fuel system Replace with recommended fuel Replace filter See your Polaris dealer Possible Rich Fuel Mixture Cause Overuse of choke Fuel is very high octane Incorrect jetting Solution Inspect, clean and/or replace spark plugs Replace with lower octane fuel See your Polaris dealer 118