Adjusting The Valve Clearance - Yamaha YZ250F Owner's Service Manual

3. Install:
• Digital tachometer
Digital tachometer
90890-06760
YU-39951-B
TIP
Get the high tension cord "1" of the ignition coil
pinched in the detector "a" of the digital tachom-
eter.
1
a
4. Measure:
• Engine idling speed
Out of specification  Regulate.
Engine idling speed
1900–2100 r/min
5. Adjust:
• Engine idling speed
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Turn the starter knob/idle screw "1" in the di-
rection of "a" or "b" to make an adjustment.
b
a
Engine idling speed  De-
Direction "a"
creases.
Engine idling speed  In-
Direction "b"
creases.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SM5089

ADJUSTING THE VALVE CLEARANCE

TIP
• This section is intended for those who have
basic knowledge and skill concerning the ser-
vicing of Yamaha motorcycles (e.g., Yamaha
dealers, service engineers, etc.). Those who
have little knowledge and skill concerning ser-
vicing are requested not to undertake inspec-
tion, adjustment, disassembly, or reassembly
only by reference to this manual. It may lead
to servicing trouble and mechanical damage.
• Make sure that the valve clearance is
checked or adjusted while the engine is cold
(at room temperature).
• While the valve clearance is checked or ad-
justed, make sure that the piston is positioned
1
in the top dead center (TDC).
1. Remove:
• Seat
a
• 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.
• ECU
2. Remove:
• Spark plug
• Cylinder head cover
Refer to "CAMSHAFT" on page 5-11.
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw "2"
• O-ring
1
4. Check:
• Valve clearance
Out of specification  Regulate.
3-17
1
Valve clearance (cold)
Intake
0.13–0.20 mm (0.0051–0.0079 in)
Exhaust
0.17–0.24 mm (0.0067–0.0094 in)
ENGINE
2