Yamaha GT1 Service Manual page 50

ENGINE -
Carburetor
A. Checking the Carburetor
1
I
Float
Remove the float and shake it
to check if gaso-
line is inside. If fuel leaks into the float while
the engine is running, the float chamber fuel
level will rise and make the fuel mixture too
rich.
Replace the float if it is deformed or
leaking.
21 FI oat valve
Replace the float valve if its seating end is worn
with a step or if it is scratched. Check the
float valve spring for fatigue. Depress the float
valve with your finger, and make sure that it
properly seats against the valve seat. If the
float valve spring is weakened, fuel will over-
flow, flooding the float chamber while the gas
is on.
3) Overflowing
If fuel overflows, check the carburetor as de-
scribed in 1) and 2) above. If neither 1) nor
2} cures the overflowing, it may be caused by
dirt or dust in the fuel preventing the float
valve from seating properly. If any dirt or dust
is found, clean the carburetor, petcock :'.lnr! n.qc::
tank.
Valve seat
L
Float valve
Fig. 4-18-2
Fuel
Dust
Fig. 4-18-3
-44-
4)
Cleaning the carburetor
Dis~ssemble the carburetor, and wash all its
parts in a suitable solvent.
Then blow all the parts off with compressed
air. All jets and other delicate parts should be
cleaned by blowing compressed air through
them after the float blowl has been removed.
Fig. 4-18-4
B. Idle Mixture-Idle Speed Adjustments
The idle mixture adjustment should be set exactly
to factory specifications. First, turn the air screw in
until it lightly seats, then back it out 1-3/4 turns.
Next, adjust the throttle stop so that the engine idles
at 1 ,250
~
1,350 rpm.