Yamaha VK540EF Service Manual page 113

Trouble
Poor performance Starter valve is left
at high speeds:
open
S Power loss
Clogged air vent
S Poor acceleration
Poor acceleration
Clogged or loose
main air jet
Clogged fuel line
Dirty fuel tank
Air leaks into the
fuel line
Low fuel pump
performance
Clogged fuel filter
Clogged intake
Abnormal Lean mixture
combustion:
Dirty carburetors
S Backfiring S Backfiring
Dirty or clogged
fuel line
Overflow: Clogged air vent
S Poor idling
Clogged float
S Poor performance
valve
at lo at low, mid-range, mid range
Scratched or
and high speeds
unevenly worn
S Excessive fuel
float
consumption
valve or valve seat
S Hard starting S Hard starting
Broken float
S Power loss
Power loss
S Poor acceleration
Incorrect float
level
CARBURETOR TUNING
Diagnosis
Return the starter lever to its seated position so
that the starter valve is fully closed.
Remove and clean the air vent.
S Remove the main jet, clean it with compressed
air, and then install it.
S Make sure that the main jet is fully tightened.
Clean or replace the fuel line.
Clean the fuel tank.
Tighten or replace the fuel line joint.
Repair or replace the fuel pump.
Replace the fuel filter.
Remove any obstructions (e.g., ice).
Clean and adjust the carburetors.
Clean the carburetors.
Clean or replace the fuel line.
Clean the air vent.
S Disassemble and clean the float valve.
S Do not scratch the valve seat.
S Clean or replace the float valve and valve seat.
S The valve seat and body must be replaced
as a set.
Replace the float.
Check and, if necessary, replace the following
parts:
S Float tang
S Float (entire assembly)
S Arm pin
2-37
INSP
ADJ
Adjustment