Measure the outside diameter [D] of the seating pattern on the valve seat.
If the outside diameter is too large or too small, repair the seat (see Valve Seat Repair).
Valve Seating Surface Outside Diameter Standard:
Exhaust 23.9
24.1 mm (0.941
0.949 in.)
Intake 30.4
30.6 mm (1.197
1.205 in.)

Measure the seat width [E] of the portion where there is no build-up carbon (white portion) of the valve seat with a vernier caliper.
Good [F]
If the width is too wide [G], too narrow [H] or uneven [J], repair the seat (see Valve Seat Repair).
Valve Seating Surface Width Standard:
Exhaust 0.8
1.2 mm (0.03
0.05 in.)
Intake 0.5
1.0 mm (0.02
0.04 in.)
Valve-to-Guide Clearance Measurement (Wobble Method)
Valve Seat RepairECU Removal
NOTICE
Never drop the ECU especially on a hard surface.
Such a shock to the ECU can damage it.
Remove the upper air cleaner housing (see Air Cleaner
Element Replacement in the Periodic Maintenance chapter).
Lift up the ECU [A] with rubber protector [B] to disconnect
the connectors [C]. ...
Air Switching Valve (Service Code 64)
Air Switching Valve Removal/Installation
Refer to the Air Switching Valve Removal/Installation in
the Engine Top End chapter.
Air Switching Valve Inspection
Refer to the Air Switching Valve Unit Test in the Electrical
System chapter.
If the air switching valve [A] is normal, check ...
Spring Preload Adjustment
Remove the rear shock absorber from the frame (see
Rear Shock Absorber Removal).
Loosen the locknut and turn out the adjusting nut to free
the spring.
Special Tools - Hook Wrench T=3.2 R37: 57001-1539
Hook Wrench R=35: 57001-1580
To adjust the spring preload, turn in the adjusting n ...