VALVE SEAT INSPECTION/REFACING
Clean the intake and exhaust valves thoroughly to remove carbon deposits.
Apply light coating of Prussian Blue to the valve seat.
Tap the valves and seats using a rubber hose or other hand-lapping tool.
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Remove the valve and inspect the valve seat face. The valve seat contact should be within the specified width and even all around the circumference.
STANDARD:
IN: 1.1-1.3 mm (0.04-0.05 in)
EX: 1.3-1.5 mm (0.05-0.06 in)
SERVICE LIMIT:
IN/EX: 2.0 mm (0.08 in)
If the seat width is not within specification, reface the valve seat (page 9-31).
Inspect the valve seat face for:
• Uneven seat width:
- Replace the valve and reface the valve seat.
• Damaged face:
- Replace the valve and reface the valve seat.
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The valves cannot be ground. If a valve face is burned or badly worn or if it contacts the seat unevenly, replace the valve. |
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• Contact area (too high or too low) - Reface the valve seat.
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Follow the refacmg manufacturer's operating instructions. |
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Valve seat cutters/grinders or equivalent valve seat refacing equipment are recommended to correct worn valve seats.
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If the contact area is too high on the valve, the seat must be lowered using a 32° flat cutter.
If the contact area is too low on the valve, the seat must be raised using a 60° interior cutter.
Use a 45° seat cutter, remove any roughness or irregularities from the seat.
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Reface the seat with a 45° cutter whenever a valve guide is replaced. |
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TOOLS:
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07780-0010400 7780- 0010800 7781- 0010101 07781-0010400 |
Seat cutter, 35 mm (IN) Seat cutter, 33 mm (EX) Cutter holder, 5.5 mm (IN) Cutter holder, 5.0 mm (EX)
or equivalent commercially available in U. S.A.
Use a 32° flat cutter, remove 1/4 of the existing valve seat material.
TOOLS:
Flat cutter, 36 mm (IN) 07780-0013500
Flat cutter, 33 mm (EX) 07780-0012900
Cutter holder, 5.5 mm (IN) 07781-0010101
Cutter holder, 5.0 mm (EX) 07781-0010400
or equivalent commercially available in U. S.A.
Use a 60° interior cutter, remove 1/4 of the existing valve seat material.
TOOLS:
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07780-0014100 7780- 0014700 7781- 0010101 07781-0010400 |
Interior cutter, 37.5 mm (IN) Interior cutter, 34 mm (EX) Cutter holder, 5.5 mm (IN) Cutter holder, 5.0 mm (EX)
or equivalent commercially available in U. S.A.
Using a 45° seat cutter, cut the seat to proper width. Make sure all pitting and irregularities are removed. Refinish if necessary.
STANDARD:
IN: 1.1 - 1.3 mm (0.04 - 0.05 in)
EX: 1.3-1.5 mm (0.05-0.06 in)
INTAKE SIDE.
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After refacing, wash the cylinder head and valve.
• Do not lap the intake valves. They are titanium and have a thin oxide coating. Lapping will damage this coating.
• Use only new intake valves.
EXHAUST SIDE:
After cutting the exhaust seats, apply lapping compound to the exhaust valve face, and lap the exhaust valve using light pressure.
After lapping, wash any residual compound off the cylinder head and valve.
• Excessive lapping pressure may deform or damage the seat.
• Change the angle of the lapping tool frequently to prevent uneven seat wear.
• Do not allow any lapping compound to enter the guides.
