Polaris 2005 Sportsman MV7 Service Manual page 133

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
S
Restricted tank vent, or routed
S
improperly
Fuel lines or fuel valve restricted
S
Fuel filter plugged
S
Carburetor vent line(s) restricted
S
Plugged or restricted inlet needle
S
and seat screen or inlet passage
Clogged jets or passages
S
Float stuck, holding inlet needle
S
closed or inlet needle stuck
Float level too low
S
Fuel pump inoperative
S
Air leak at impulse line
S
Restricted impulse line (kinked,
S
pinched)
Intake air leak (throttle shaft, intake
S
ducts, airbox or air cleaner cover)
Ruptured vacuum slide diaphragm,
S
Vacuum slide stuck closed or sticky
Improper spring
S
Jet needle position incorrect
S
Incorrect pilot screw adjustment
S
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
S
duct)
Air filter dirty/plugged
S
Choke plunger sticking, incorrectly
S
adjusted choke
Choke cable binding or improperly
S
routed
Incorrect pilot air/fuel screw
S
adjustment
Faulty inlet needle and seat
S
Faulty inlet needle seat O-Ring
S
Float level too high
S
Poor fuel quality (old fuel)
S
FUEL SYSTEM / CARBURETION
Loose jets
S
Worn jet needle/needle jet or other
S
carburetor parts
Dirty carburetor (air bleed
S
passages or jets)
Weak or damaged vacuum piston
S
return spring
Fouled spark plug
S
POOR IDLE
Idle Too High
Idle adjusted improperly/idle
S
mixture screw damaged
Sticky vacuum slide
S
Throttle cable sticking, improperly
S
adjusted, routed incorrectly
Choke cable sticking, improperly
S
adjusted, routed incorrectly
Plugged or restricted idle jet
S
Idle Too Low
Choke cable bending or incorrectly
S
adjusted
Idle speed set incorrectly
S
Idle mixture screw misadjusted or
S
damaged
Belt dragging
S
Ignition timing incorrect
S
Worn jet needle/needle jet
S
Plugged or restricted idle jet
S
Erratic Idle
Choke cable bending or incorrectly
S
adjusted
Throttle cable incorrectly adjusted
S
Air leaks, dirty carburetor passages
S
(pilot circuit)
Pilot mixture screw damaged or
S
adjusted incorrectly
Tight valves
S
Ignition timing incorrect
S
Belt dragging
S
Dirty air cleaner
S
Engine worn
S
Spark plug fouled
S
Idle speed set incorrectly (speed
S
limiter)
Worn jet needle/needle jet
S
Plugged or restricted idle jet
S
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