Disassembly; Inspection; Assembly - Yamaha BR250F Service Manual

B. Disassembly
1. Carefully remove the jets, float, etc.
Never, however, disassemble the throttle
valve or the throttle shaft. The threads
of the throttle shaft have been crimped
so the screw will not come lose. Once
the throttle valve is disassembled, it will
be very difficult to reassemble it correct-
ly. The original characteristics of this
carburetor will be difficult to reproduce,
thus performance will be adversely
affected.
2. Carefu Ily clean all parts. Blow the jets
and passages clear with compressed air.
Use a soft brush to clean the outside
surfaces so nothing will be scratched or
damaged. Do not use a wire or any such
object to clear a jet. This will deform the
jet and reduce performance.
3. Remove the carbon from the throttl-e
valve and adjacent area. Take care not to
scratch the throttle valve or bore.
C. Inspection
1. Inspect all jets and passages. They must
be clear.
2. Check the mating surfaces for wear.
Replace jets as required.
3. Check the float valve for damage. If
either the float seat or float needle are
damaged, replace both parts.
4. Check the pilot screw for carbon
deposits; check the threads for wear.
Clean and replace the jet as required.
D. Assembly
Use new O-rings when assembling the carbure-
tor. Thoroughly grease the contact surfaces of
the throttle shaft. Be sure all moving parts in
the carbu retor operate smoothly.
1. Install the throttle stop screw with its
spring. For adjustment (Refer to 3-2, E
"Low Speed Tuning".)
2. Install the main jet and the slow jet.
3. Install the slow adjuster with its spring.
For adjustment (Refer to 3-2, E "Low
Speed Tuning".)
4. Install the clip onto the float needle.
5. Hook the float needle clip onto the float
tang. Install the float, and insert the
float needle into the float valve.
3-2
6. Measure the float level.
a. Incline the carburetor approximately 20
or 30 degrees until the float valve just
barely closes. The float should be resting
on the float needle, but not compressing
the spring.
b. Measure the distance from the carbure-
tor body to the top of the float.
Float height:
15
±
2 mm (0.59
±
0.08 in)
1. Float height
c. If the float height is not within specifica-
tion, examine the valve seat and the float
needle. If either is worn, replace them
both. If both are fine, adjust the float
height by bending the tang on the float.
d. Reinstall the float and recheck the float
height.
8. Reassemble the float.