Yamaha VX700F Manuel D'atelier page 125

Trouble
Poor performance at Clogged or loose pilot jet
mid-range speeds:
• Momentary slow re-
sponse to the throttle
• Poor acceleration
Lean mixture
Poor performance at Clogged air vent
normal speeds:
Clogged or loose main jet
• Excessive fuel con-
sumption
• Poor acceleration
Overflow
Poor performance at Starter valve is left open
high speeds:
• Power loss
Clogged air vent
• Poor acceleration
Clogged or loose main air
jet
Clogged fuel line
Dirty fuel tank
Air leaks into the fuel line
Low fuel pump perfor-
mance
Clogged fuel filter
Clogged intake
Abnormal combustion: Lean mixture
Dirty carburetors
• Backfiring
Dirty or clogged fuel line
Overflow: Clogged air vent
• Poor idling
Clogged float valve
• Poor performance at
low, mid-range, and
Scratched or unevenly
high speeds
worn float valve or valve
• Excessive fuel con-
seat
sumption
Broken float
• Hard starting
Incorrect float level
• Power loss
• Poor acceleration
CARBURETOR TUNING
Diagnosis
• Remove the pilot jet, clean it with compressed air, and
then install it.
• Make sure that the pilot jet is fully tightened.
Overhaul the carburetors.
Remove the air vent hose and clean it.
• Remove the main jet, clean it with compressed air, and
then install it.
• Make sure that the main jet is fully tightened.
Check and, if necessary, clean the float and float valve.
Return the starter lever to its seated position so that the
starter valve is fully closed.
Remove and clean the air vent.
• Remove the main jet, clean it with compressed air, and
then install it.
• 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.
• Disassemble and clean the float valve.
• Do not scratch the valve seat.
• Clean or replace the float valve and valve seat.
• The valve seat and body must be replaced as a set.
Replace the float.
Check and, if necessary, replace the following parts:
• Float tang
• Float (entire assembly)
• Arm pin
2-46
INSP
ADJ
Adjustment