Refacing The Valve And Valve Seat; Checking Rocker Arms And The Rocker Shaft - Westerbeke 9.0 BCG Technical Manual

Refacing the Valve and Valve Seat
To reface the valve and cylinder head valve seats, follow
the steps below.
1. For the intake port in the cylinder head, use a 30° cut-
ter to bring back the valve seat's shoulder. Then use
a 45° cutter to recondition the valve seat contact face.
2. For the exhaust port in the cylinder head, use a 20° cut-
ter to bring back the valve seat's shoulder. Then use
a 45° cutter to recondition the valve seat contact face.
3. Grind each valve's contact face to 45°. Match each
( ) are Exhaust Side
valve to its respective cylinder head port and check to ensure that both the cylinder's contact face and
the valve's contact face are perfectly matched.
4. After each valve is reconditioned, hand lap each valve onto its seat with a good brand of lapping com-
pound.
5.
Remeasure the contact width of both the valves and
each cylinder head valve seat and ensure that they
conform to the following specifications.
Contact Width (Both Intake and Exhaust)
BCG 4.0KW 0.047 - 0.063 inches
(1.2 -1.6 mm)
BCG 6.5KW and BTG 9.0KW
0.039 - 0.071 inches
(1.0 -1.8 mm)
Checking Rocker Arms and the Rocker Shaft
Contact width
1. Check each component of the rocker arm assembly for damage or cracks. If necessary, replace it with
a new one.
2. Check to see that the oil passages of the rocker arm and shaft are open. If any clogs are found, remove
them or replace the unit.
3.
Measurethe clearance between each rocker arm's bore
and the shaft. If this measurement exceeds the allow-
able limit, replace the worn rocker arm bushings and
shaft.
Arm Inner Diameter: 0.6300 - 0.6307 inches
(16.000 - 16.018 mm)
Shaft Outer Diameter: 0.6283 - 0.6293 inches
(15.958 -15.984 mm)
(See next page)
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