Yamaha TT-R90(V), Owner'S Service Manual, Page: 204 / 390

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ENG
CARBURETOR
EC464401
Jet needle
1. Inspect:
• Jet needle
1
Bends/wear
→
Replace.
• Clip groove
Free play exists/wear
→
Replace.
• Clip position
Float height
1. Measure:
• Float height
a
Out of specification
→
Adjust.
Standard clip position:
No.2 Groove
Float height:
15.5 ~ 16.5 mm (0.61 ~ 0.65 in)
Measurement and adjustment steps:
• Hold the carburetor in an upside down
position.
NOTE:
• Slowly tilt the carburetor in the opposite
direction, then take the measurement
when the needle valve aligns with the float
arm.
• If the carburetor is level, the weight of the
float will push in the needle valve, resulting
in an incorrect measurement.
• Measure the distance between the mating
surface of the float chamber and top of the
float using a vernier calipers.
NOTE:
The float arm should be resting on the nee-
dle valve, but not compressing the needle
valve.
• If the float height is not within specification,
inspect the valve seat and needle valve.
• If either is worn, replace them both.
• If both are fine, adjust the float height by
bending the float tab
1
on the float.
• Recheck the float height.