Service Manual

2-14 PERIODIC MAINTENANCE
Periodic Maintenance Procedures
•
Coat the seat with machinist’s dye.
•
Fit a 45° cutter [A] to the holder and slide it into the valve
guide.
○
Resurface the valve seat with a 45° cutter, removing only
enough material to produce a smooth and concentric
seat.
CAUTION
Do not grind the seat too much. Overgrinding will
reduce valve clearance by sinking the valve into the
head. If the valve sinks too far into the head, it will
be impossible to adjust the clearance, and the cylin-
der head must be replaced. Do not turn the cutter
counterclockwise or drop it against the seat, or it
will be dulled.
•
Use a 32° seat cutter [A] to narrow the seat width to the
standard width.
○
Turn the seat cutter one turn at a time while pressing down
very lightly. Check the seat width after each turn.
CAUTION
The 32° cutter removes material very quickly.
Check the seat width frequently to prevent over
grinding.
NOTE
○
Keep the seat width as close as possible to the standard
width.
•
Make a light contact on the valve seat with the 45° cutter
to remove any possible burrs at the edge of the seat.
•
After resurfacing the seat, inspect for even valve seating.
○
Apply a machinist’s dye to the valve face, insert the
valve, and snap it closed against the seat several times.
The valve surface should show good contact all the way
around. Be sure the valve seat is centered on the valve
face. The position of the valve in the seat is evident after
lapping the valve.
If the seat does not make proper contact, lap the valve
into seat with a lapper.
•
Coat the face of valve sparingly with a fine lapping com-
pound.
•
Use the lapping tool [A], to grip top of the valve [B]. Rotate
the valve in a circular motion to lap the valve to the seat.
•
Lift the valve slightly from the seat every 8 to 10 strokes,
continue lapping operation until a uniform ring appears
around entire surface of the valve face.