Yamaha WR250R, Service Manual

Page: 76 / 364

ENGINE
3-4
EAS20471
ENGINE
EAS20520
ADJUSTING THE VALVE CLEARANCE
The following procedure applies to all of the
valves.
NOTE:
●
Valve clearance adjustment should be made
on a cold engine, at room temperature.
●
When the valve clearance is to be measured or
adjusted, the piston must be at top dead center
(TDC) on the compression stroke.
1. Remove:
●
Seat
●
Side cover (left/right)
●
Air scoop (left/right)
Refer to “GENERAL CHASSIS” on page 4-1.
●
Fuel tank
Refer to “FUEL TANK” on page 7-1.
2. Drain:
●
Coolant
Refer to “CHANGING THE COOLANT” on
page 3-20.
3. Remove:
●
Throttle cable
●
Clutch cable
Refer to “CAMSHAFT” on page 5-6.
4. Remove:
●
Ignition coil assembly
●
Spark plug
Refer to “CAMSHAFT” on page 5-6.
5. Remove:
●
Throttle bodies
Refer to “THROTTLE BODIES” on page 7-4.
●
Air vent hose (Air induction)
●
Cylinder head cover
Refer to “CAMSHAFT” on page 5-6.
6. Remove:
●
Timing mark accessing screw “1”
●
Crankshaft end cover “2”
7. Measure:
●
Valve clearance
Out of specification
→
Adjust.
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a. Turn the crankshaft counterclockwise.
b. Align TDC mark “a” of the generator rotor with
mark “b” of the generator rotor cover.
c. Measure the valve clearance with a thickness
gauge “1”.
Out of specification
→
Adjust.
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8. Adjust:
●
Valve clearance
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove:
●
Cam chain tensioner
●
Camshaft cap
●
Intake camshaft
●
Exhaust camshaft
NOTE:
●
Refer to “CAMSHAFT” on page 5-6.
1
2
Valve clearance (cold)
Intake
0.13 – 0.20 mm (0.0051 – 0.0079 in)
Exhaust
0.23 – 0.30 mm (0.0091 – 0.0118 in)
Special thickness gauge
90890-03180
Feeler gauge set
YU-26900-9
a
b
1