Yamaha VK540EF Service Manual page 112

ESS00091
Troubleshooting
Trouble
Hard starting
Poor idling:
S Poor performance
at low speeds
S Poor acceleration
S Slow response to
Sl t
throttle
S Engine tends to S Engine tends to
stall
Poor performance
at mid-range
speeds:
S Momentary slow
res onse to response to
the throttle
S Poor acceleration
Poor performance
at normal speeds:
S Excessive fuel
consumption
S Poor acceleration S Poor acceleration
CARBURETOR TUNING
Diagnosis
Insufficient fuel Add gasoline.
Excessive use of Return the starter lever to its seated position so
the starter or that the starter valve is fully closed.
choke
S Check and, if necessary, clean the fuel tank air
Fuel passage is
clogged or frozen
S Check and, if necessary, clean the carburetor
S Clean the float chamber of any ice or water.
Overflow Adjust the fuel level.
Improper idling Adjust the engine idle speed.
speed adjustment Refer to "Low speed tuning".
Damaged pilot Replace the pilot screw.
screw
Clogged bypass Clean the bypass hole.
hole
S Remove the pilot jet, clean it with compressed
Clogged or loose
pilot jet
S Make sure that the pilot jet is fully tightened.
Air leaking into the Retighten the clamp screws on the carburetor
carburetor joint joints.
Defective starter Clean or replace the starter valve seat.
valve seat
Overflow Adjust the fuel level.
S Remove the pilot jet, clean it with compressed
Clogged or loose
pilot jet
S Make sure that the pilot jet is fully tightened.
Lean mixture Overhaul the carburetors.
Clogged air vent Remove the air vent hose and clean it.
S Remove the main jet, clean it with compressed
Clogged or loose
main jet
S Make sure that the main jet is fully tightened.
Overflow Check and, if necessary, clean the float and
float valve.
Adjustment
vent, the fuel filter and all of the fuel passages.
air vents, fuel passages and the float valve.
air and then install it.
air, and then install it.
air, and then install it.
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INSP
ADJ