Honda CRF250X User Manual

Adjustments for Competition 129
Carburetor Adjustment & Tuning Tips
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
(3)
(1)
(7)
(6)
(2)
(5)
(4)
(3)
(2)
(1)
(5)
(4)
(2)
(4)
(7)
(6)
(5)
(1)
(3)
250X_104-129.qxd 08.7.3 10:14 ページ129

Honda CRF250X Specifications

General

Engine Type	249cc liquid-cooled single-cylinder four-stroke
Bore and Stroke	78.0mm x 52.2mm
Compression Ratio	12.9:1
Induction	Keihin 37mm flat-slide carburetor
Ignition	CDI
Transmission	Wide-ratio five-speed
Front Suspension	47mm inverted Showa cartridge fork with 16-position rebound and 16-position compression damping adjustability; 12.4 inches travel
Front Brake	Single 240mm disc with twin-piston caliper
Rear Brake	Single 240mm disc
Front Tire	80/100-21
Rear Tire	100/100-18
Trail	113mm (4.4 inches)
Wheelbase	58.3 inches
Seat Height	37.7 inches
Fuel Capacity	1.9 gallons
Final Drive	520 chain; 13T/51T
Rake	27.5 degrees
Rear Suspension	Pro-Link Showa single shock with spring preload, 17-position rebound damping adjustability, and 13-position compression damping adjustability; 12.4 inches travel
Curb Weight	254 lbs (Includes all standard equipment, required fluids and a full tank of fuel—ready to ride)