2010 YAMAHA WR 250F engine

[x] Cancel search: engine

Page 104 of 232

YAMAHA WR 250F 2010  Owners Manual 5-1
RADIATOR
ENGINE
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles 
(e.g., Yamaha dealers, service engineers, etc.)  Those who  ha

Page 106 of 232

YAMAHA WR 250F 2010  Owners Manual 5-3
RADIATOR
HANDLING NOTE
Do not remove the radiator cap 
when the engine and radiator are 
hot. Scalding hot fluid and steam 
may be blown out under pressure, 
which could cause serious injury. 
Whe

Page 110 of 232

YAMAHA WR 250F 2010  Owners Manual 5-7
CARBURETOR
HANDLING NOTE
Do not loosen the screw (throttle 
position sensor) "1" except when 
changing the throttle position sen-
sor due to failure because it will 
cause a drop in engine perfor-

Page 120 of 232

YAMAHA WR 250F 2010  Owners Manual 5-17
CAMSHAFTS
4. Measure:• Camshaft-to-cap clearanceOut of specification →Measure 
camshaft outside diameter.
Measurement steps:
a. Install the camshaft onto the cylin- der head.
b. Position a st

Page 122 of 232

YAMAHA WR 250F 2010  Owners Manual 5-19
CYLINDER HEAD
CYLINDER HEAD
REMOVING THE CYLINDER HEADOrder Part name Qty Remarks Seat and fuel tank  Refer to "REMOVING THE SEAT, FUEL 
TANK AND SIDE COVERS" section in the 
CHAPTER 3.
Exhaust

Page 127 of 232

YAMAHA WR 250F 2010  Owners Manual 5-24
VALVES AND VALVE SPRINGS
CHECKING THE VALVE SPRINGS
1. Measure:• Valve spring free length "a"Out of specification →Replace.
2. Measure: • Compressed spring force "a"Out of specification →

Page 130 of 232

YAMAHA WR 250F 2010  Owners Manual 5-27
CYLINDER AND PISTON
a. 10 mm (0.39 in)
3. Measure:
• Ring end gapOut of specification →Replace.
You cannot measure the end gap on 
the expander spacer of the oil control 
ring. If the oil con

Page 131 of 232

YAMAHA WR 250F 2010  Owners Manual 5-28
CYLINDER AND PISTON
INSTALLING THE CYLINDER
1. Lubricate:•Piston
• Piston ring
• Cylinder
Apply a liberal coating of engine oil.
2. Install:
• Dowel pin "1"
• O-ring "2" 
Apply the lith