2003 Polaris Scrambler 50-90 Sportsman 90 Predator 90 Service Manual, Page 67Get this manual
FUEL SYSTEMCARBURETION
TROUBLESHOOTING
FUEL STARVATIONLEAN MIXTURE Symptoms: Hard start or no start, bog, backfire, popping through intakeexhaust, hesitation, detonation, low power, spark plug erosion, engine runs hot, surging, high idle, idle speed erraticNo fuel in tank Restricted tank vent, or routed improperly Fuel lines or fuel valve restricted Fuel filter plugged Carburetor vent line(s) restricted Plugged or restricted inlet needle and seat screen or inlet passage Clogged jets or passages Float stuck, holding inlet needle closed or inlet needle stuck Float level too low Intake air leakcrankcase seal throttle shaft, intake ducts, airbox or air cleaner cover) Jet needle position incorrect Incorrect pilot screw adjustment RICH MIXTURE Symptoms: Fouls spark plugs, black, sooty exhaust smoke, rough idle, poor fuel economy, engine runs rough misses, poor performance, bog, engine loads up, backfireAir intake restricted (inspect intake duct) Air filter dirtyplugged Electric choke inoperative Incorrect pilot airfuel screw adjustment Faulty inlet needle and seat Faulty inlet needle seat O-Ring Float level too high Poor fuel quality (old fuel) Loose jets Worn jet needleneedle jet or other carburetor parts Dirty carburetor (air bleed passages or jets) Fouled spark plug POOR IDLE Symptoms: Idle too highIdle adjusted improperlyidle mixture screw damaged Sticky throttle valve Throttle cable sticking, improperly adjusted, routed incorrectly IDLE TOO LOW Idle speed set incorrectly Idle mixture screw misadjusted or damaged CVT system dragging Ignition timing incorrect Worn jet needleneedle jet ERRATIC IDLE Choke not working properly Throttle cable incorrectly adjusted Air leaks, dirty carburetor passages (pilot circuit) Pilot mixture screw damaged or adjusted incorrectly Ignition timing incorrect Belt dragging Dirty air cleaner Engine worn Spark plug fouled Idle speed set incorrectly (speed limiter) Worn jet needleneedle jet