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Chapter 6 INSPECTION AND REPAIR OF BASIC ENGINE
1.9 Valve and Valve Seat - Lap
Lap the valve and valve seat whenever valve seat is refaced
or valve is replaced, or the contact surfaces fail to keep a
pressure in the pressure test after assembling.
(1) Apply a thin coat of lapping compound evenly to the
valve face.
Note:(a) Do not allow the compound to adhere to the valve
stem.
(b) Compound spreads more evenly when it is mixed
with a small amount of engine oil.
(c) Use medium-grain compound (125 to 150 mesh)
for initial lapping, then use fine-grain compound
(200 mesh) for finishing.
(2) Use a valve lapper for lapping.
Tap the valve against valve seat while rotating the valve
little by little.
(3) Clean off the compound using diesel oil.
(4) Apply engine oil to the contact surface of valve, and
finish the lapping.
(5) Apply a thin lead-free coloring paste on the valve face,
and tap the valve face against the valve seat using a
valve lapper to check for contact condition.
1.10 Valve Bridge, Bridge Cap, Valve Cotter and Valve Rotator - Inspect
(1) Inspect the contact surfaces between valve bridge and
valve stem, and the sliding surface between valve
bridge and bridge guide. If significant wear or uneven
contact is found, replace them with new ones.
(2) Check the bridge cap for wear. If significant wear is
found, replace the bridge cap with a new one.
(3) Check the valve rotator for rotation. If any defect is
found, replace the valve rotator with a new one.
(4) Inspect the contact surfaces between valve cotter and
valve stem, and valve cotter and valve rotator. If signif-
icant uneven wear or dent is found, replace them with
new ones.
6-8
Compound - Apply
Valve lapper
P/N:30091-08800
Valve and Valve Seat - Lap
Bridge cap
Valve bridge
Valve stem
Valve cotter
Valve Bridge, Bridge Cap, Valve Cotter and Valve
Rotator - Inspect
Compound
Bridge guide
Valve rotator
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