Yamaha YBR250 2007 Service Manual page 64

ADJUSTING THE VALVE CLEARANCE
b
a
3
2
6. Measure:
a. Turn the crankshaft counterclockwise.
d
b. When piston #1 is at TDC on the compression
c
NOTE:
To place the piston at the Upper Dead Center
(UDC) on the compression time, match the "I" mark
c of the sprocket camshaft with the mark d at
the cylinder head, as shown in the illustration.
c. Measure the valve clearance with a thickness
7. Adjust:
a. Loosen the locknut 1.
b. Insert the thickness gauge between the
c. Turn the adjustment screw 3 with a wrench 2
Clockwise
Counter-
clockwise
1
3-8
valve clearance
•
Out of specification
-->
Valve clearance (cold)
Intake valve
0.05 ~ 0.10mm (0.002 ~ 0.004 in)
Exhaust valve
0.08 ~ 0.13mm (0.003 ~ 0.005 in)
stroke, align the TDC mark a on the AC
magneto with the mark b on the crankcase
cover.
gauge 1.
Thickness gauge
90890-03079
Out of specification
-->
valve clearance
•
adjustment screw end and the valve rod tip.
in one of the following directions to obtain the ideal
clearance.
The clearance is increased
The clearance is decreased
Adjustment screw wrench
90890-01311
CHK
ADJ
Adjust.
Adjust.