Honda 2009 CRF450X User Manual

HONDA O/M CRF450X (Eu) 3RMEY620 00X3R-MEY-6200
Carburetor Adjustment & Tuning Tips
Adjustments for Competition 135
Accelerator Pump Circuit
The accelerator pump circuit operates when the
throttle is opened. As the throttle valve (1) opens,
the pump rod (2) depress the diaphragm (3). At
this time, the inlet check valve (4) is shut
resulting in a sharp increase in pressure in the
pump chamber (5). The outlet check valve (6)
then opens, supplying fuel to the main bore via
the accelerator nozzle (7).
(1) throttle valve (5) pump chamber
(2) pump rod (6) outlet check valve
(3) diaphragm (7) accelerator nozzle
(4) inlet check valve
Slow Circuit
Fuel is metered by the slow jet (1) and mixed
with air from the air passage (2). The mixture
enters the venturi through the bypass (3) and
pilot outlet (4) that has been metered by the pilot
screw (5).
(1) slow jet (4) pilot outlet
(2) air passage (5) pilot screw
(3) bypass
Main Circuit
Fuel is metered by the main jet (1), jet needle (2)
and needle jet (3). It is then mixed with air
coming from the air jet (4) and enters the venturi
past the needle jet.
Baffle Plate
The baffle plate (5) prevents foaming of fuel or
abnormal fuel level around the main jet.
Float Bowl
The float (6) and float valve (7) operate to
maintain a constant level of fuel in the float bowl.
(1) main jet (5) baffle plate
(2) jet needle (6) float
(3) needle jet (7) float valve
(4) air jet
(1)
(7)
(6)
(2)
(3)
(5)
(4)
(3)
(4)
(5)
(1)
(2)
(2)
(4)
(7)
(6)
(5)
(1)
(3)

Honda 2009 CRF450X Specifications

General

Engine Type	449cc liquid-cooled single-cylinder four-stroke
Bore x Stroke	96.0mm x 62.1mm
Compression Ratio	12.0:1
Induction	Keihin 40mm flat-slide carburetor
Transmission	Wide-ratio five-speed
Final Drive	#520 chain; 13T/51T
Rear Suspension	Pro-Link Showa single shock with spring preload, 17-position rebound damping adjustability, and compression damping adjustment separated into low-speed (13 positions) and high-speed (3.5 turns); 12.4-inch travel
Front Brake	Single 240mm disc with twin-piston caliper
Rear Brake	Single 240mm disc
Front Tire	80/100-21
Rear Tire	110/100-18
Wheelbase	58.3 inches
Seat Height	37.6 inches
Fuel Capacity	1.9 gallons
Front Suspension	47mm inverted Showa cartridge fork with 16-position rebound and 16-position compression damping adjustability; 12.4 inches travel
Ignition	CD with electronic advance