Service manual

ENGINE TOP END 5-33
Valves
Valve Seat Inspection
•
Remove the valve (see Valve Removal).
•
Check the valve seating surface [A] between the valve [B]
and valve seat [C].
○
Coat the valve seat with machinist’s dye.
○
Push the valve into the guide.
○
Rotate the valve against the seat with a lapping tool.
○
Pull the valve out, and check the seating pattern on the
valve head. It must be the correct width and even all the
way around.
•
Measure the outside diameter [D] of the seating pattern
on the valve seat.
If the outside diameter of the valve seating pattern is too
large or too small, repair the seat (see Valve Seat Repair).
Valve Seating Surface Outside Diameter
Exhaust:
25.2 ∼ 25.4 mm (0.992 ∼ 1.000 in.)
Inlet:
29.4 ∼ 29.6 mm (1.157 ∼ 1.165 in.)
NOTE
○
The valve stem and guide must be in good condition, or
this check will not be valid.
If the valve seating pattern is not correct, repair the seat
(see Valve Seat Repair).
•
Measure the seat width [E] of the portion where there is
no build-up carbon (white portion) of the valve seat with
vernier calipers.
If the width is too wide, too narrow or uneven, repair the
seat (see Valve Seat Repair).
[F] Good
[G] Too Wide
[H] Too Narrow
[J] Uneven
Valve Seating Surface Width
Exhaust: 0.5 ∼ 1.0 mm (0.02 ∼ 0.04 in.)
Inlet: 0.5 ∼ 1.0 mm (0. 02 ∼ 0.04 in.)
Valve Seat Repair (Valve Lapping)
•
Using the valve seat cutters [A], repair the valve seat.
Special Tools - Valve Seat Cutters:
Exhaust Valves:
Valve Seat Cutter, 45° -
27.5: 57001-1114
Valve Seat Cutter, 32° -
28: 57001-1119
Valve Seat Cutter, 60° -
30: 57001-1123
Inlet Valves:
Valve Seat Cutter, 45° -
30: 57001-1187
Valve Seat Cutter, 32° -
33: 57001-1199
Valve Seat Cutter, 60° -
30: 57001-1123
Holder and Bar:
Valve Seat Cutter Holder,
5: 57001-1208 [B]
Valve Seat Cutter Holder Bar: 57001-1128 [C]
If the manufacturer’s instructions are not available, use
the following procedure.