Fuel System / Carburetion - Troubleshooting
FUEL STARVATION/LEAN MIXTURE
Symptoms: Hard start or no start, bog, backfire, popping through intake/exhaust, hesitation, detonation, low power, spark plug erosion, engine runs hot, surging, high idle, idle speed erratic.
- No 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 leak (crankcase 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, backfire.
- Air intake restricted (inspect intake duct)
- Air filter dirty/plugged
- Electric choke inoperative
- Incorrect pilot air/fuel 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 needle/needle jet or other carburetor parts
- Dirty carburetor (air bleed passages or jets)
- Fouled spark plug
POOR IDLE
Symptoms: Idle too high.
- Idle adjusted improperly/idle 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 needle/needle 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 G Belt dragging
- Dirty air cleaner
- Engine worn
- Spark plug fouled
- Idle speed set incorrectly (speed limiter)
- Worn jet needle/needle jet
