Page 1
5. FUEL SYSTEM
5-0
Mongoose/KXR 250
5
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FUEL SYSTEM
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SERVICE INFORMATION -------------------------------------------- 5- 2
TROUBLESHOOTING ------------------------------------------------- 5- 3
FUEL TANK------------------------------------------------------------- 5- 4
FUEL VALVE REMOVAL -------------------------------------------- 5- 4
THROTTLE VALVE ----------------------------------------------------- 5- 7
CARBURETOR ---------------------------------------------------------- 5- 8
AIR CLEANER ---------------------------------------------------------- 5-12
5
Page 2
5. FUEL SYSTEM
5-1
Mongoose/KXR 250
Page 3
5. FUEL SYSTEM
5-2
Mongoose/KXR 250
SERVICE INFORMATION
GENERAL INSTRUCTIONS
• Do not bend or twist control cables. Damaged control cables will not operate smoothly.
• When disassembling fuel system parts, note the locations of O-rings. Replace them with new
ones during reassembly.
• Before float chamber disassembly, loosen the drain screw to drain the residual gasoline into a
clean container.
• After the carburetor is removed, plug the intake manifold side with a clean shop towel to prevent
foreign matters from entering.
• When cleaning the carburetor air and fuel jets, the O-rings and diaphragm must be removed first to
avoid damage. Then, clean with compressed air.
• When the motorcycle is not used for over one month, drain the residual gasoline from the float
chamber to avoid erratic idling and clogged slow jet due to deteriorated fuel.
SPECIFICATIONS
Item
Standard
Type
PD
Venturi dia.
f22
Float level
14.8mm
Main jet No.
98
Adjust method
Piston
Idle speed
1500±100rpm
Throttle grip free play
1_ 4mm
Air screw opening
11/8±1/2
Gasoline is very dangerous. When working with gasoline, keep sparks and flames away
from the working area.
Gasoline is extremely flammable and is explosive under certain conditions. Be sure to work
in a well-ventilated area.
Page 4
5. FUEL SYSTEM
5-3
Mongoose/KXR 250
SPECIAL TOOL
Float level gauge
TROUBLESHOOTING
Engine cranks but won’t start Engine lacks power
• No fuel in tank • Clogged air cleaner
• No fuel to carburetor • Faulty carburetor
• Cylinder flooded with fuel • Faulty ignition system
• No spark at plug
• Clogged air cleaner Lean mixture
• Intake air leak • Clogged carburetor fuel jets
• Improper throttle operation • Float level too low
• Intake air leak
Engine idles roughly, stalls or runs poorly • Clogged fuel tank cap breather hole
• Excessively used choke • Kinked or restricted fuel line
• Ignition malfunction
• Faulty carburetor Rich mixture
• Poor quality fuel • Float level too high
• Lean or rich mixture • Clogged air jets
• Incorrect idle speed • Clogged air cleaner
Misfiring during acceleration
• Faulty ignition system
• Faulty carburetor
Backfiring at deceleration
• Float level too low
• Incorrectly adjusted carburetor
• Faulty exhaust muffler
Page 5
5. FUEL SYSTEM
5-4
Mongoose/KXR 250
FUEL TANK
REMOVAL
Remove the seat, right and left side frame
cover (See page 2-3) and center frame cover
(See page 2-5).
Switch the fuel valve “OFF”.
Disconnect the fuel tube from carburetor and
remove two screws at the fuel valve holder.
Remove the two bolts and two nuts at the
fuel tank, then remove the fuel tank.
INSTALLATION
Reverse the “FUEL TANK REMOVAL”
procedures.
FUEL VALVE
REMOVAL
Remove the screw and then remove control
switch.
Disconnect all fuel tubes and remove the two
screws, then remove fuel valve.
Warning
Nuts
Fuel Tank
Screw
Fuel Valve
Screws
Fuel Tube
• Keep sparks and flames away from the
work area.
• Wipe off any spilled gasoline.
Control Switch
Screws
Fuel Valve
• Keep sparks and flames away from the
work area.
• Drain gasoline into a clean container.
°Ø
Fuel Tube
Fuel Tubes
Page 6
5. FUEL SYSTEM
5-5
Mongoose/KXR 250
DISASSEMBLY
Remove the two screws on the retaining ring
and then remove retaining ring.
Remove the washer and control shaft.
Remove the rubber gasket from the fuel valve
body.
INSPECTION
Inspect the fuel valve body for dirt and clog.
Clean if necessary.
Replace the rubber gasket with new ones if
they are damaged or deteriorated.
Replace the O-rings with new ones if they
are damaged or deteriorated.
ASSEMBLY
Reverse the “DISASSEMBLY” procedures.
Install rubber gasket, control shaft, washer
and retaining ring.
Fuel Valve Body
Control Shaft
Rubber Gasket
Retaining Ring
Washer
Screws
Control Shaft
O-ring
• Aligning the tab on the control shaft
with the outlet duct in the fuel valve
body.
• Aligning the tab on the retaining ring
with the outlet duct in the fuel valve
body.
°Ø
Tab
Outlet Duct
Outlet Duct
Tab
Page 7
5. FUEL SYSTEM
5-6
Mongoose/KXR 250
INSTALLATION
Reverse the “FUEL VALVE REMOVEAL”
procedures.
Connect all fuel tube.
Reserve Fuel Tube
Main Fuel Tube
Outlet Fuel Tube
Page 8
5. FUEL SYSTEM
5-7
Mongoose/KXR 250
THROTTLE VALVE
DISASSEMBLY
Remove the fuel tank. (Refer to “FUEL
TANK” section in the chapter 5)
Remove the carburetor cap.
Pull out the throttle valve.
Compress the spring to disconnect the
throttle cable by hand.
Remove the spring from the throttle valve
Carburetor Cap
Spring
Throttle
Throttle Cable
Page 9
5. FUEL SYSTEM
5-8
Mongoose/KXR 250
Pry off the needle retainer and remove the jet
needle.
Check the throttle valve and jet needle for
wear or damage.
ASSEMBLY
Reverse the “DISASSEMBLY” procedures.
Install the throttle valve into the carburetor
body.
CARBURETOR
REMOVAL
Remove the fuel tank and carburetor cap.
(Refer to “FUEL TANK” and “THROTTLE
VALVE DISASSEMBLY” section in the
chapter 5)
Loosen the drain screw to drain the gasoline
from the float chamber.
Loosen the screw on the lock plate for
disconnect the choke cable.
Throttle
Needle Retainer
Jet Needle
Clip
Fuel Drain Plug
Choke Cable
Screw
Align the groove in the throttle valve
with the throttle stop screw on the
carburetor body.
°Ø
Throttle Stop Screw
Groove
• Keep sparks and flames away from the
work area.
• Drain gasoline into a clean container.
°Ø
Page 10
5. FUEL SYSTEM
5-9
Mongoose/KXR 250
Remove the two bolts at the air cleaner case.
Loosen the air cleaner connecting tube band
screw.
Remove the two carburetor lock nuts
attaching the inlet pipe.
Remove the carburetor
DIS AS SEMBLY
Remove the float chamber attaching three
screws and remove the float chamber.
Remove the jet holder.
Pull out the float pin, then remove float and
float valve.
Jet Holder
Bolts
Band
Screws
Float Valve
Float Pin
Float
Nuts
Float Chamber
Page 11
5. FUEL SYSTEM
5-10
Mongoose/KXR 250
Remove the main jet, needle jet holder, and
needle jet.
Remove the slow jet.
Remove the air screw and throttle stop
screw.
CAUTIONS!
Remove the two screws and the air cut-off
valve cover.
Screws
Air Screw
Slow Jet
Main Jet
Throttle Stop Screw
Spring
Washer
O-ring
Air Screw
Throttle Stop Screw
Spring
Slow Jet
Main Jet
Needle Jet Holder
Needle Jet
• Be careful not to damage the jets and
jet holder when removing them.
• Before removal, turn the throttle stop
screw and air screw in and count the
number of turns until they seat lightly
and then make a note of this.
• Do not force the screw against its seat
to avoid seat damage.
• Be sure to install the O-ring in the
reverse order of removal.
°Ø
Page 12
5. FUEL SYSTEM
5-11
Mongoose/KXR 250
Remove the spring, diaphragm and O-rings.
Inspect the diaphragm and spring for wear or
damage.
CARBURETOR CLEANING
Blow compressed air through all passages of
the carburetor body.
FLOAT/FLOAT VALVE INSPECTION
Inspect the float valve seat for wear or
damage.
Inspect the float for damage or fuel level
inside the float chamber.
FUEL RESERVOIR O-RING CHECK
Remove the O-ring.
INSPECTION
Inspect the check the O-ring for damage.
Replace with new ones if necessary
Spring
Diaphragm
Cover
O-ring
Float Valve
Float Valve Seat
O-ring
Page 13
5. FUEL SYSTEM
5-12
Mongoose/KXR 250
ASSEMBLY
Install the slow jet.
Install the needle jet, needle jet holder and
main jet.
Install the throttle stop screw and air screw
Install the spring, diaphragm and O-rings.
Install the float valve, float and float pin.
FLOAT LEVEL INSPECTION
Turn the carburetor upside down so that the
float will go down to make the float valve
contact the float valve seat.
Then slowly tilt the carburetor and measure
the float level with the float level gauge while
the float pin just contacts with float valve.
Float Level: 14.8mm
When adjusting, carefully bend the float pin.
Check the float for proper operation.
Install the jet holder, aligning the jet holder
groove with the carburetor tab and then
install the float chamber.
INSTALLATION
Reverse the “ CARBURETOR REMOVAL”
procedures.
AIR CLEANER
Refer to the “AIR CLEANER” section in the
chapter 3 for air cleaner replacement and
cleaning.
• When installing the air screw, return it
to the original position as noted during
removal
• After the carburetor is installed, be sure
to perform the Exhaust Emission Test.
°Ø
Jet Holder
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