Service Manual

5-12 ENGINE TOP END
Valves
Valve Guide Inside Diameter
•
Use a small bore gauge or a micrometer to measure the
inside diameter [A] of t he valve guides [B] at three places
down the length of the guides.
If the measurement is more than the service limit, replace
the cylinder head with a new one.
Valve Guide Inside Diameter
Service Limit (IN, EX) : 6.08 mm (0.239 in.)
Valve Spring Inspection
•
Inspect the valve spring for pitting, cracks, rusting, and
burns. Replace the spring if necessary.
•
Measure the free length [A] of the spring.
If the measurement is less than the service limit, replace
the spring.
Valve Spring Free Length
Service Limit: 33.5 mm (1.32 in.)
Automatic Compression Release (ACR) Device
Inspection
The ACR reduces the compression of the cylinder in or-
der to facilitate the revolution of the crankshaft during the
starting of the engine.
•
Remove:
Rocker Cover (see Cylinder Head Assembly Removal)
Spark Plug (see Electrical System chapter)
•
Check whether the valves have the specified clearance
(see Periodic Maintenance chapter).
•
Slowly turn the crankshaft in the direction and observe the
movement of the exhaust valve [A] and the rocker arm [B].
Immediately after the intake valve has closed, the rocker
arm should push open the exhaust valve to attain a lift that
is greater. If the exhaust valve does not lift to that height,
the ACR that is provided on the camshaft is faulty (see
Camshaft/Crankshaft chapter).
Exhaust Valve Lift Height Service Limit by ACR
Standard: 0.9 mm (0.04 in.)