Yamaha 2003 YZ450F Service Manual

1 - 18
GEN
INFO
STARTING AND BREAK-IN
STARTING AND BREAK-IN
WARNING
Never start or run the engine in a closed
area. The exhaust fumes are poisonous;
they can cause loss of consciousness and
death in a very short time. Always operate
the machine in a well-ventilated area.
CAUTION:
● The carburetor on this motorcycle has a
built-in accelerator pump. Therefore,
when starting the engine, do not operate
the throttle or the spark plug will foul.
● Unlike a two-stroke engine, this engine
cannot be kick started when the throttle is
open because the kick starter may kick
back. Also, if the throttle is open the air/
fuel mixture may be too lean for the
engine to start.
● Before starting the machine, perform the
checks in the pre-operation check list.
STARTING A COLD ENGINE
1. Inspect the coolant level.
2. Turn the fuel cock to “ON”.
3. Shift the transmission into neutral.
4. Fully open the cold starter knob 1.
5. Kick the kick starter.
WARNING
Do not open the throttle while kicking the
kick starter. Otherwise, the kick starter may
kick back.

Yamaha 2003 YZ450F Specifications

General

Bore x Stroke	95.0mm x 63.4mm
Compression Ratio	12.5:1
Ignition	CDI
Transmission	5-speed
Final Drive	Chain
Front Tire	80/100-21
Rear Tire	110/90-19
Wheelbase	58.5 inches
Ground Clearance	14.6 inches
Front Suspension	48mm Kayaba inverted telescopic fork; fully adjustable, 11.8-in travel
Rear Suspension	Kayaba single shock; fully adjustable, 12.4-in travel
Front Brake	250mm disc
Rear Brake	245mm disc
Fuel Capacity	1.8 gal
Seat Height	39.1 inches
Width	32.5 inches
Height	51.4 inches
Dry Weight	220 lb
Engine Type	449cc liquid-cooled DOHC 4-stroke; 5 titanium valves