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3-34 DISASSEMBLY, REASSEMBLY, INSPECTION, AND MAINTENANCE
Valve System
Use a wire brush to remove the deposits from the valve stem. If the
valve stem does not move smoothly in the valve guide or the stem
shows abnormal wear, replace the valve with a new one.
•
Using a micrometer, measure the valve stem diameter in several
places.
If the measured value is smaller than the service limit, replace the
valve with a new one.
Valve Stem Diameter Service Limit (minimum)
Intake Valve Exhaust Valve
FE120, 170: 5.430 mm (0.2138 in) 5.415 mm (0.2132 in)
FE250: 5.930 mm (0.2335 in) 5.915 mm (0.2329 in)
FE290, 350, 400: 6.930 mm (0.2728 in) 6.915 mm (0.2722 in)
•
Support both ends of the valve stem on V blocks [A] as shown in the
diagram. Place a dial gauge [B] against the center, and gently rotate
the valve stem to measure the bend of the stem (by reading the entire
fluctuation of the dial gauge).
Valve Stem Bend Service Limit (maximum)
– for both Intake and Exhaust
FE120, 170: 0.05 mm (0.0020 in)
FE250, 290, 350, 400: 0.03 mm (0.0012 in)
If the measured value is greater than the service limit, replace the
valve with a new one.
Valve Spring Inspection
•
Inspect the valve spring for the presence of corrosion or cracks, and
replace it with a new one if necessary.
•
Using a vernier caliper, measure the free length of the valve spring.
Valve Spring Free Lenght Service Limit (minium)
- for both Intake and Exhaust
FE120, 170: 31.8 mm (1.25 in)
FE250, 290: 32.8 mm (1.29 in)
FE350, 400: 38.1 mm (1.50 in)
If the free length is shorter than the service limit, replace the valve
spring with a new one.
NOTE
During reassembly, beware that the spring pitch is smaller at the
valve seat side of the valve spring on the FE250, 290, 350, and
400. For both intake and exhaust valves.
A: Valve Spring