Yamaha SXV70ERG, Supplementary Service Manual

Page: 36 / 173

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