Yamaha WR250F(N) Owner's Service Manual page 204

VALVE CLEARANCE INSPECTION AND ADJUSTMENT
3. Remove:
Right radiator
Refer to "RADIATOR" section in the
CHAPTER 4.
Carburetor
Refer to "CARBURETOR" section in
the CHAPTER 4.
Spark plug
Upper engine bracket
Cylinder head cover
Refer to "CAMSHAFTS" section in the
CHAPTER 4.
4. Remove:
Timing mark accessing screw 1
Crankshaft end accessing screw 2
O-ring
5. Check:
Valve clearance
Out of specification
Valve clearance (cold):
Intake valve:
0.10 ~ 0.15 mm (0.0039 ~ 0.0059 in)
Exhaust valve:
0.17 ~ 0.22 mm (0.0067 ~ 0.0087 in)
3 - 20
INSP
ADJ
Adjust.