2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 113Get this manual
ENGINE TROUBLESHOOTING
Spark Plug Fouling
Spark plug cap loose or faulty Choke cable adjustment or plungercable sticking Foreign material on choke plunger seat or plunger Incorrect spark plug heat range or gap Carburetor inlet needle and seat worn Jet needle andor needle jet worn or improperly adjusted Excessive carburetor vibration (loose or missing needle jet locating pins) Loose jets in carburetor or calibration incorrect for altitudetemperature Incorrect float level setting PVT system calibrated incorrectly or components worn or mis-adjusted Fuel quality poor (old) or octane too high Low compression Restricted exhaust Weak ignition (loose coil ground, faulty coil, stator, or ETC switch) ETC switch mis-adjusted Restricted air filter (main or pre-cleaner) or breather system Improperly assembled air intake system Restricted engine breather system Oil contaminated with fuel Restricted oil tank vent
Engine Engine Turns Over But Fails to Start No fuel Dirt in fuel line or filter Fuel will not pass through fuel valve Fuel pump inoperativerestricted Tank vent plugged Carb starter circuit Engine flooded Low compression (high cylinder leakage) No spark (Spark plug fouled) Engine Does Not Turn Over Dead battery Starter motor does not turn Engine seized, rusted, or mechanical failure Engine Runs But Will Not Idle Restricted carburetor pilot system Carburetor misadjusted Choke not adjusted properly Low compression Crankcase breather restricted Engine Idles But Will Not Rev Up Spark plug fouledweak spark Broken throttle cable Obstruction in air intake Air box removed (reinstall all intake components) Incorrect or restricted carburetor jetting ETC switch limiting speed Reverse speed limiter limiting speed Carburetor vacuum slide stickingdiaphragm damaged Incorrect ignition timing Restricted exhaust system