Engine

ENGINE

EAS20470

ENGINE                                                                 Valve clearance (cold)
                                                                        Intake
EAS20490                                                                  0.15–0.22 mm (0.0059–0.0087 in)
ADJUSTING THE VALVE CLEARANCE                                           Exhaust
The following procedure applies to all of the                             0.18–0.25 mm (0.0071–0.0098 in)
valves.
NOTE:                                                     ▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
                                                          a. Turn the crankshaft clockwise.
• Valve clearance adjustment should be made
                                                          b. When piston #1 is at TDC on the compres-
  on a cold engine, at room temperature.
                                                             sion stroke, align the TDC mark “a” on the
• When the valve clearance is to be measured or
                                                             pickup rotor with the crankcase mating sur-
  adjusted, the piston must be at top dead center
                                                             face “b”.
  (TDC) on the compression stroke.
                                                          NOTE:
1. Remove:                                                TDC on the compression stroke can be found
 • Rider seat                                             when the camshaft lobes are turned away from
 • Right side cowling                                     each other.
   Refer to “GENERAL CHASSIS” on page 4-1.
 • Fuel tank
   Refer to “FUEL TANK” on page 7-1.
 • T-bar
   Refer to “GENERAL CHASSIS” on page 4-1.
 • Air cut-off valve                                               b
   Refer to “AIR INDUCTION SYSTEM” on
   page 7-11.                                                      a
 • Thermostat inlet pipe 1
   Refer to “THERMOSTAT” on page 6-6.
2. Disconnect:
 • Throttle cables
3. Remove:                                                                 IN              EX
 • Spark plugs
 • Cylinder head cover
 • Cylinder head cover gasket
   Refer to “CAMSHAFTS” on page 5-12.
4. Remove:
 • Hose holder “1”
 • Lead holders “2”
 • Pickup rotor cover “3”
                                                          c. Measure the valve clearance with a thickness
                                                             gauge “1”.

           1                                                   1

           3                        2

5. Measure:
 • Valve clearance
   Out of specification → Adjust.                         NOTE:
                                                          • If the valve clearance is incorrect, record the
                                                            measured reading.

                                                    3-6
                                                                                                  ENGINE

• Measure the valve clearance in the following               ▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
  sequence.                                                  a. Remove the valve lifter “1” and the valve pad
                                                                “2” with a valve lapper “3”.
   Valve clearance measuring sequence                                   Valve lapper
    Cylinder #1 → #2 → #4 → #3                                           90890-04101
                                                                        Valve lapping tool
                                                                         YM-A8998

                                                             NOTE:
                                                             • Cover the timing chain opening with a rag to
                                                               prevent the valve pad from falling into the
                                                               crankcase.
                                                             • Make a note of the position of each valve lifter
                                                               “1” and valve pad “2” so that they can be in-
                                                               stalled in the correct place.
 A. Front
d. To measure the valve clearances of the other
   cylinders, starting with cylinder #1 at TDC,
   turn the crankshaft clockwise as specified in
   the following table.

 A. Degrees that the crankshaft is turned
    clockwise
 B. Cylinder
 C. Combustion cycle

      Cylinder #2                   180°                     b. Calculate the difference between the speci-
                                                                fied valve clearance and the measured valve
      Cylinder #4                   360°                        clearance.
      Cylinder #3                   540°                        Example:
                                                                Specified valve clearance = 0.15–0.22 mm
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲                                (0.0059–0.0087 in)
6. Remove:                                                      Measured valve clearance = 0.25 mm
 • Camshafts                                                    (0.0098 in)
NOTE:                                                           0.25 mm (0.0098 in) - 0.22 mm (0.0087 in) =
• Refer to “CAMSHAFTS” on page 5-12.                            0.03 mm (0.001 in)
• When removing the timing chain and cam-                    c. Check the thickness of the current valve pad.
  shafts, fasten the timing chain with a wire to re-         NOTE:
  trieve it if it falls into the crankcase.                  The thickness “a” of each valve pad is marked in
7. Adjust:                                                   hundredths of millimeters on the side that touch-
 • Valve clearance                                           es the valve lifter.

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