2012 YAMAHA YZ250F height

4-13
CARBURETOR
c. If the float height is not within
specification, inspect the valve
seat and needle valve.
d. If either is worn, replace them
both.
e. If both are fine, adjust the float
height by bending the float tab "b"
on the float.
f. Recheck the float height.
CHECKING THE FLOAT
1. Inspect:
• Float "1"
Damage→Replace.
CHECKING THE STARTER
PLUNGER
1. Inspect:
• Cold starter plunger "1"
• Hot starter plunger "2"
Wear/damage→Replace.
CHECKING THE ACCELERATOR
PUMP
1. Inspect:
• Diaphragm (accelerator pump)
"1"
• Spring (accelerator pump) "2"
• Accelerator pump cover "3"
• O-ring "4"
• Push rod "5"
Tears (diaphragm)/damage→Re-
place.
Dirt→Clean.2. Inspect:
• Throttle shaft "1"
• Spring "2"
• Lever 1 "3"
• Spring 1 "4"
• Lever 2 "5"
• Spring 2 "6"
Dirt→Clean.
ASSEMBLING THE CARBURETOR
1. Install:
• Cold starter plunger "1"
2. Install:
•Pilot air jet "1"
3. Install:
• Spring 1 "1"
• Lever 1 "2"
To lever 2 "3".
Make sure the spring 1 fits on the
stopper "a" of the lever 2.
4. Install:
• Spring 2 "1"
To lever 2 "2".
5. Install:
• Push rod link lever assembly "1"
Make sure the stopper "a" of the
spring 2 fits into the recess "b" in the
carburetor.
6. Install:
• Washer "1"
• Circlip "2"
7. Install:
• Spring "1"
To throttle shaft "2".
Install the bigger hook "a" of the
spring fits on the stopper "b" of the
throttle shaft pulley.
8. Install:
• Throttle shaft assembly "1"
• Washer (metal) "2"
• Washer (resin) "3"
• Valve lever "4"

4-15
CARBURETOR
17. Install:
• O-ring "1"
• Valve lever housing cover "2"
• Bolt (valve lever housing cover)
"3"
18. Install:
• Carburetor breather hose "1"
Install the carburetor breather hoses
to the carburetor so that the hoses do
not bend near where they are in-
stalled.
ADJUSTING THE ACCELERATOR
PUMP TIMING
Adjustment steps:
In order for the throttle valve height
"a" to achieve the specified value,
tuck under the throttle valve plate "1"
the rod "2" etc. with the same outer di-
ameter as the specified value.
a. Fully turn in the accelerator pump
adjusting screw "3".
b. Check that the link lever "4" has
free play "b" by pushing lightly on
it.c. Gradually turn out the adjusting
screw while moving the link lever
until it has no more free play.
INSTALLING THE CARBURETOR
1. Install:
• Carburetor joint "1"
2. Install:
• Carburetor "1"
Install the projection "a" between the
carburetor joint slots.
3. Install:
• Hot starter plunger "1"
4. Tighten:
• Bolt (carburetor joint) "1"
• Bolt (air filter joint) "2"5. Install:
• Throttle cable (pull) "1"
• Throttle cable (return) "2"
6. Adjust:
• Throttle grip free play
Refer to "ADJUSTING THE
THROTTLE GRIP FREE PLAY"
section in the CHAPTER 3.
7. Install:
• Throttle cable cover "1"
• Bolt (throttle cable cover) "2"
8. Install:
• Throttle position sensor lead cou-
pler "1"
• Clamp "2"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2. Throttle valve height:
0.7 mm (0.028 in)
Carburetor joint:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Hot starter plunger:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (carburetor joint):
3 Nm (0.3 m•kg, 2.2
ft•lb)
Bolt (air filter joint):
3 Nm (0.3 m•kg, 2.2
ft•lb)
Throttle cable (pull):
4 Nm (0.4 m•kg, 2.9
ft•lb)
Throttle cable (return):
11 Nm (1.1 m•kg, 8.0
ft•lb)
Bolt (throttle cable cov-
er):
4 Nm (0.4 m•kg, 2.9
ft•lb)

4-24
VALVES AND VALVE SPRINGS
REMOVING THE VALVE LIFTER
AND VALVE COTTER
1. Remove:
• Valve lifter "1"
• Pad "2"
Identify each lifter "1" and pad "2" po-
sition very carefully so that they can
be reinstalled in their original place.
2. Check:
• Valve sealing
Leakage at the valve seat→In-
spect the valve face, valve seat
and valve seat width.
Checking steps:
a. Pour a clean solvent "1" into the
intake and exhaust ports.
b. Check that the valve seals prop-
erly.
There should be no leakage at the
valve seat "2".
3. Remove:
• Valve cotter
Attach a valve spring compressor "1"
between the valve spring retainer and
the cylinder head to remove the valve
cotters.
CHECKING THE VALVE
1. Measure:
• Stem-to-guide clearance
Out of specification→Replace the
valve guide.
2. Replace:
• Valve guide
Replacement steps:
To ease guide removal, installation
and to maintain correct fit heat the
cylinder head in an over to 100 °C
(212 °F).
a. Remove the valve guide using a
valve guide remover "1".b. Install the new valve guide using a
valve guide remover "1" and valve
guide installer "2".
c. After installing the valve guide,
bore the valve guide using a valve
guide reamer "3" to obtain proper
stem-to-guide clearance.
After replacing the valve guide reface
the valve seat.
Valve spring compres-
sor:
YM-4019/90890-04019
Stem-to-guide clearance = valve
guide inside diameter "a" -
valve stem diameter "b"
Clearance (stem to
guide):
Intake:
0.010–0.037 mm
(0.0004–0.0015 in)
:0.08 mm
(0.003 in)
Exhaust:
0.025–0.052 mm
(0.0010–0.0020 in)
:0.10 mm
(0.004 in)Valve guide installation
height "a":
Intake:
11.8–12.2 mm
(0.46–0.48 in)
Exhaust:
11.3–11.7 mm
(0.44–0.46 in)
Valve guide remover:
Intake:4.0 mm (0.16 in)
YM-4111/90890-04111
Exhaust:4.5 mm (0.18
in)
YM-4116/90890-04116
Valve guide installer:
Intake:4.0 mm (0.16 in)
YM-4112/90890-04112
Exhaust:4.5 mm (0.18
in)
YM-4117/90890-04117
Valve guide reamer:
Intake:4.0 mm (0.16 in)
YM-4113/90890-04113
Exhaust:4.5 mm (0.18
in)
YM-4118/90890-04118

5-13
FRONT BRAKE AND REAR BRAKE
INSTALLING THE FRONT BRAKE
MASTER CYLINDER
1. Install:
• Brake master cylinder "1"
• Brake master cylinder bracket "2"
• Bolt (brake master cylinder brack-
et) "3"
• Install the bracket so that the arrow
mark "a" face upward.
• First tighten the bolts on the upper
side of the brake master cylinder
bracket, and then tighten the bolts
on the lower side.
2. Install:
• Brake lever "1"
• Bolt (brake lever) "2"
• Nut (brake lever) "3"
Apply the silicone grease on the
brake lever sliding surface, bolt and
tip of the push rod.
INSTALLING THE REAR BRAKE
MASTER CYLINDER
1. Install:
• Copper washer "1"
• Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake master cylinder.
2. Install:
• Brake master cylinder "1"
• Bolt (brake master cylinder) "2"3. Install:
• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
• Clip "5"
Apply the lithium soap base grease
on the bolt, O-ring and brake pedal
bracket.
4. Install:
•Pin "1"
• Washer "2"
• Cotter pin "3"
After installing, check the brake pedal
height. Refer to "ADJUSTING THE
REAR BRAKE" section in the CHAP-
TER 3.
INSTALLING THE FRONT BRAKE
HOSE
1. Install:
• Copper washer "1"
• Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Bolt (brake master cylin-
der bracket):
9 Nm (0.9 m•kg, 6.5
ft•lb)
Bolt (brake lever):
6 Nm (0.6 m•kg, 4.3
ft•lb)
Nut (brake lever):
6 Nm (0.6 m•kg, 4.3
ft•lb)
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Bolt (brake master cylin-
der):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (brake pedal):
26 Nm (2.6 m•kg, 19
ft•lb)
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)