Yamaha QT 50F Service Manual page 32

4-1. CARBURETOR
A. Inspection and Repair
1. Remove following parts
a) Pilot jair screw
b) Throttle stop screw
c) Floatchamber
d) Float I
e) Needle valve
f) Main jet
g) Needle jet
h) Pilot jet
2. Wash carburetor in petroleum base sol-
vent. Wash all associated parts.
3. Using high pressure air, blow out all
passages and jets.
4. Inspect needle for signs of excessive
• wear or I foreign particles. Replace as
required.
,'5-::.
Inspect pilot air screw for signs of ex-
cessive wear or foreign particles. Re-
place as required.
6. Install float chamber.
7. Remove needle out of seat in throttle
valve (slide). Inspect for signs of bend-
ing, scratches or wear. Replace as
required.
8. Check throttle valve (slide) for signs of
wear. Insert into carburetor body and
check for free movement. If slide or
body is out of round causing slide to
stick, replace slide or body as necessary.
9. Install throttle valve and needle assem-
bly in carburetor mixing chamber.
10. Install mixing chamber top.
11. Re-install carburetor. Check position
and routing of all tubes. Check tight-
ness of all fittings. Make sure carburetor
is mounted in a level position (Refer to
CABLE ROUTING DIAGRAM).
12. After installation, readjust throttle cable
and Autolube pump cable. See direc-
tions in Chapter 2, Section 2-3-A. and
2-3-C.
4-2. REED VALVE ASSEMBLY
A. Inspection
1. Handling the reed valve
The reed valve is operated by changes
in crankcase pressure and by the inertia
force of the fuel-air stream. It is a high-
precision piece, and therefore, it must
be handled with special care.
2. Storage
The reed valve must be stored in a clean
and dry place and must be kept off the
sun. Particularly, it must be kept free
from salt. Avoid touching the valve.
3. Inspect reed petals for signs of fatigue
and cracks. Reed petals should fit flush
or nearly flush against neoprene seats.
If in doubt as to sealing ability, apply
suction to carburetor side of assembly.
Leakage should be slight to moderate.
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