Yamaha TW200 Service Manual page 102

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I_N_S_P_EC_T_I_O_N_A_N_D_R_E_PA_IR_I~GI~I
NOTE: _
- Always replace the guide if the valve is replaced.
- Always replace the oil seal if the valve is
removed.
VALVE SEAT
1. Clean the valve face and valve seat to remove
carbon deposits.
2. Inspect:
-Valve seat
Pitting/Wear--+> Reface the valve seat.
3. Measure:
-Valve seat width
®
Out of specification--+> Reface valve seat.
Valve Seat Width:
Intake 0.9-1.1
mm
(0.035-0.043 in)
Exhaust 0.9 -1.1 mm (0.035 - 0.043 in)
Measurement steps:
-Apply the Mechanic's bluing dye (Dykem)
CD
to the valve face.
-Install the valve into the cylinder head.
- Press the valve through the valve guide and
onto the valve seat to make a clear pattern.
- Measure the valve seat width. Wherever the
valve seat and valve face made contact, blu-
ing will have been removed.
-If the valve seat width is too wide, too nar-
row, or seat had not centered, the valve seat
must be refaced.
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