fuel type YAMAHA YZ250F 2010 Owners Manual

1-15
TORQUE-CHECK POINTS
TORQUE-CHECK POINTS
Concerning the tightening torque, refer to "TIGHTENING TORQUES" section in the CHAPTER 2.
Frame constructionFrame to rear frame
Combined seat and fuel tank Fuel tank to frame
Exhaust system Silencer to rear frame
Engine mounting Frame to engine
Engine bracket to engine
Engine bracket to frame
Steering Steering stem to handlebar Steering stem to frame
Steering stem to upper bracket
Upper bracket to handlebar
Suspension Front Steering stem to front forkFront fork to upper bracket
Front fork to lower bracket
Rear For link type Assembly of links
Link to frame
Link to rear shock absorber
Link to swingarm
Installation of rear shock absorber Rear shock absorber to frame
Installation of swingarm Tightening of pivot shaft
Wheel Installation of wheel Front Tightening of wheel axle
Tightening of axle holder
Rear Tightening of wheel axle Wheel to rear wheel sprocket
Brake Front Brake caliper to front fork
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to handlebar
Tightening of bleed screw
Tightening of brake hose holder
Rear Brake pedal to frame Brake disc to wheel
Tightening of union bolt
Brake master cylinder to frame
Tightening of bleed screw
Tightening of brake hose holder
Fuel system Fuel tank to fuel cock
Lubrication system Tightening of oil hose clamp

2-1
GENERAL SPECIFICATIONS
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model name:YZ250FZ (USA, CDN, AUS, NZ)
YZ250F (EUROPE, ZA)
Model code number: 17D5 (USA,CDN)
17D6 (EUROPE)
17D8 (AUS, NZ, ZA)
Dimensions: USA, CDN EUROPE AUS, NZ, ZA
Overall length 2,159 mm (85.00
in) 2,168 mm (85.35
in)2,166 mm (85.28
in)
Overall width 825 mm (32.48 in)←←
Overall height 1,303 mm (51.30
in) 1,304 mm (51.34
in)←
Seat height 988 mm (38.90 in) 991 mm (39.02 in) 990 mm (38.98 in)
Wheelbase 1,466 mm (57.72
in) 1,473 mm (57.99
in)←
Minimum ground clearance 375 mm (14.76 in) 377 mm (14.84 in) 376 mm (14.80 in)
Weight: With oil and fuel 102.0 kg (224.9 lb)
Engine: Engine type Liquid cooled 4-stroke, DOHC
Cylinder arrangement Single cylinder, forward inclined
Displacement 250 cm
3 (8.80 Imp oz, 8.45 US oz)
Bore × stroke 77.0 × 53.6 mm (3.03 × 2.11 in)
Compression ratio 13.5 : 1
Starting system Kickstarter
Lubrication system: Dry sump
Oil type or grade: Engine oil Recommended brand: YAMALUBE
SAE10W-30, SAE10W-40, SAE10W-50
SAE15W-40, SAE20W-40 or SAE20W-50
API service SG type or higher,
JASO standard MA
Oil capacity: Engine oilPeriodic oil change 0.95 L (0.84 Imp qt, 1.00 US qt)
With oil filter replacement 1.05 L (0.92 Imp qt, 1.11 US qt)
Total amount 1.20 L (1.06 Imp qt, 1.27 US qt)
Coolant capacity (including all routes): 1.00 L (0.88 Imp qt, 1.06 US qt)
Air filter: Wet type element
Fuel: Type Premium unleaded gasoline only with a research octane
number of 95 or higher.
Tank capacity 6.4 L (1.4 Imp gal, 1.69 US gal)
2

7-1
ENGINE
TUNING
ENGINE
CARBURETOR SETTING
• The air/fuel mixture will vary de-pending on atmospheric conditions.
Therefore, it is necessary to take
into consideration the air pressure,
ambient temperature, humidity,
etc., when adjusting the carburetor.
• Perform a test run to check for prop- er engine performance (e.g., throt-
tle response) and spark plug(-s)
discoloration or fouling. Use these
readings to determine the best pos-
sible carburetor setting.
It is recommended to keep a record of
all carburetor settings and external
conditions (e.g., atmospheric condi-
tions, track/surface conditions, lap
times) to make future carburetor set-
ting easier.
• The carburetor is a part of the fuel line. Therefore, be sure to in-
stall it in a wellventilated area,
away from flammable objects
and any sources of fire.
• Never look into the carburetor in- take. Flames may shoot out from
the pipe if the engine backfires
while it is being started. Gasoline
may be discharged from the ac-
celerator pump nozzle when the
carburetor has been removed.
• The carburetor is extremely sen-sitive to foreign matter (dirt,
sand, water, etc.). During instal-
lation, do not al low foreign mat-
ter to get into the carburetor.
• Always handle the carburetor and its components carefully.
Even slight scratches, bends or
damage to carburetor parts may
prevent the carburetor from
functioning correctly. Carefully
perform all servicing with the ap-
propriate tools and without ap-
plying excessive force.
• When the engine is stopped or when riding at no load, do not
open and close the throttle un-
necessarily. Otherwise, too
much fuel may be discharged,
starting may become difficult or
the engine may not run well. • After installing the carburetor,
check that the throttle operates
correctly and opens and closes
smoothly.
ATMOSPHERIC CONDITIONS AND
CARBURETOR SETTINGS
The air density (i.e., concentration of
oxygen in the air) determines the rich-
ness or leanness of the air/fuel mix-
ture.
• Higher temperature expands the air with its resultant reduced density.
• Higher humidity reduces the amount of oxygen in the air by so
much of the water vapor in the
same air.
• Lower atmospheric pressure (at a
high altitude) reduces the density of
the air.
EFFECT OF SETTING PARTS IN
RELATION TO THROTTLE VALVE
OPENING
A. Closed
B. Fully open
1. Pilot screw/pilot jet
2. Throttle valve cutaway
3. Jet needle
4. Main jet CONSTRUCTION OF
CARBURETOR AND SETTING
PARTS
The FLATCR carburetor has a prima-
ry main jet. This type of main jet is
perfect for racing machines since it
supplies an even flow of fuel, even at
full load. Use the main jet and the jet
needle to set the carburetor.
The FLATCR carburetor is manufac-
tured with a pilot screw. The pilot
screw adjustment ranges from fully
closed throttle to 1/4 open throttle.
1. Jet needle
2. Pilot air jet
3. Needle jet
4. Main jet
5. Pilot jet
6. Pilot screw
ADJUSTING THE MAIN JET
The richness of the air-fuel mixture at
full throttle can be set by changing the
main jet "1".
If the air-fuel mixture is too rich or too
lean, the engine power will drop, re-
sulting in poor acceleration.
Effects of changing the main jet
(reference)
A. Idle
B. Fully open
1. #182
2. #178
3. #180
Air
tem p. Hu-
midi- ty Air
pres- sure
(alti-
tude) Mix-
ture Set-
ting
High High Low
(high) Rich-
er Lean-
er
Low Low High
(low) Lean-
er Rich-
er
Standard main jet #180
7