2010 Polaris Sportsman 850 Service Manual, Page 157Get this manual
ENGINE Engine Turns Over But Fails To Start No fuel Dirt in fuel line, filter, or injectors Fuel pump inoperativerestricted Fuel valve off or restricted flow Tank vent plugged or pinched Engine flooded Low compression (high cylinder leakage) No CPS signal (debris on CPS pole, damaged CPS causing incorrect air gap) No spark (spark plug fouled) ignition component failure 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 fuel system Low compression (valves incorrectly adjusted) Crankcase breather restricted Engine Idles But Will Not Accelerate Spark plug fouledweak spark Broken throttle cable Air intake obstructed Air box removed (reinstall all intake components) Reverse speed limiter limiting speed Incorrect ignition timing Restricted exhaust system Camshaft worn excessively PVT not operating properly Engine Has Low Power Spark plug fouled Cylinder, piston, ring, or valve wear or damage (check compression) PVT not operating properly Restricted exhaust muffler Camshaft worn excessively Piston FailureScoring Lack of lubrication Dirt entering engine through cracks in air filter or ducts Engine oil dirty or contaminated (water) Excessive Smoke and Carbon Buildup Excessive piston-to-cylinder clearance Worn rings, piston, or cylinder Worn valve guides or seals Restricted breather Air filter dirty or contaminated Low Compression No valve clearance Valve not seating properly (bent valve or carbondebris accumulated on sealing surface) Cylinder head gasket leak Cylinder or piston worn Piston rings worn, leaking, broken, or sticking Bent valve or stuck valve Valve spring broken or weak Rocker arm sticking Backfiring Fouled spark plug or incorrect plug or plug gap Speed limiter system malfunction Exhaust system air leaks Ignition system faulty: Spark plug cap crackedbroken Ignition coil faulty Ignition switch circuit faulty Poor connections in ignition system Ignition timing incorrect Sheared flywheel key Valve sticking