3-28 ENGINE
VALVE FACE WEAR
• Visually inspect each valve face for wear. Replace any valve
with an abnormally worn face. The thickness of the valve face
decreases as the face wears. Measure the valve face
T. If it
is out of specification, replace the valve with a new one.
Valve head thickness
T:
Service Limit: 0.5 mm (0.02 in)
VALVE SPRING
The force of the coil spring keeps the valve seat tight. Weak-
ened spring result in reduced engine power output, and often
account for the chattering noise coming from the valve mecha-
nism.
• Check the valve spring for proper strength by measuring its
free length and also by the force required to compress it.
• If the spring length is less than the service limit, or if the force
required to compress the spring does not fall within the range
specified, replace the spring.
[ 09900-20102: Vernier calipers
Valve spring free length (IN & EX): Service limit:
40.6 mm (1.60 in)
Valve spring tension (IN & EX): Standard:
136 – 156 N, 13.6 – 15.6 kgf/33.4 mm
(30.0 – 33.4 lbs/1.31 in)
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