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5. FUEL SYSTEM AGILITY 50
5
5
5-0
5. FUEL SYSTEM AGILITY 50
Ignition Switch
B
Regulator
/Rectifier
W Fuse
CDI Unit
L/Y Y
12V Battery
Y
Resistor
G/B
G
Lighting
System 5
5W
Auto Bystarter
5-1
5. FUEL SYSTEM AGILITY 50
SERVICE INFORMATION.......................5-2 ACCELERATING PUMP .......................5-10
TROUBLESHOOTING..............................5-3 CARBURETOR INSTALLATION.........5-11
CARBURETOR REMOVAL.....................5-4 PILOT SCREW ADJUSTMENT ............5-12
AUTO BYSTARTER .................................5-4 FUEL TANK............................................5-13
AIR CUT-OFF VALVE .............................5-6 FUEL UNIT .............................................5-14
VACUUM CHAMBER ..............................5-6 AIR CLEANER .......................................5-14
FLOAT CHAMBER...................................5-8
SERVICE INFORMATION
GENERAL INSTRUCTIONS
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.
· When disassembling the carburetor, be sure to service the vacuum piston and float chamber.
· 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 assembly.
· 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.
· Remove the vacuum diaphragm before cleaning the carburetor air and fuel passages with
compressed air to avoid damaging the vacuum diaphragm.
· 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
Venturi dia. (mm) 20
Type CVK
Float level (mm) 17
Main jet Commonly: #82 Speed limits vehicle: #80
Slow jet #35
Idle speed 2000rpm±100
Throttle grip free play 26mm
Pilot screw opening 2±1/2
5-2
5. FUEL SYSTEM AGILITY 50
TROUBLESHOOTING
Engine is hard to start Misfiring during acceleration
· No spark at plug ( Section 15) · Faulty ignition system
· Compression too low · Lean mixture
· No fuel to carburetor · Faulty accelerating pump
-Clogged fuel filter Engine idles roughly, stalls or runs poorly
-Restricted fuel line · Clogged fuel system
-Faulty float valve · Ignition malfunction
-Incorrectly adjusted float level · Rich or lean mixture
· Engine flooded with fuel · Contaminated fuel
-Clogged air cleaner · Intake air leak
-Fuel overflowing · Incorrect idle speed
· Intake air leak · Incorrectly adjusted pilot screw
· Contaminated fuel · Clogged idle system or auto bystarter passages
· Faulty auto bystarter · Incorrectly adjusted float level
· Clogged idle system or auto bystarter passages Lean mixture
Rich mixture · Clogged fuel jets
· Faulty auto bystarter · Faulty float valve
· Faulty float valve · Float level too low
· Float level too high · Clogged fuel system
· Clogged air jets · Intake air leak
· Dirty air cleaner · Improper vacuum piston operation
· Flooded carburetor · Improper throttle operation
Backfiring at deceleration
· Lean mixture in idle system
· Improper air cut-off valve operation
5-3
5. FUEL SYSTEM AGILITY 50
CARBURETOR REMOVAL
Remove the frame right side cover. ( 2-4)
Disconnect the auto bystarter wire
connector.
Remove the met-in box. ( 2-3)
Auto Bystarter Wire Auto Bystarter
Loosen the drain screw and drain the fuel
from the float chamber.
Disconnect the fuel tube and vacuum tube at
the carburetor.
Fuel Tube
Loosen the throttle cable adjusting nut and Air Cleaner Connecting Intake Manifold
lock nut, and disconnect the throttle cable Tube Band Band
from the carburetor.
Loosen the carburetor intake manifold band
and air cleaner connecting tube band screws
and then remove the carburetor.
Throttle Cable Adjusting Nut Lock Nut
AUTO BYSTARTER
OPERATION INSPECTION
Measure the resistance between the auto
bystarter wire terminals.
Resistance: 10 max. (10 minutes
minimum after stopping the engine)
If the reading is not within the limit, replace
the auto bystarter with a new one.
5-4
5. FUEL SYSTEM AGILITY 50
Vacuum Pump
Connect a hose to the fuel enriching circuit of
the carburetor. Connect the auto bystarter
yellow wire to the positive (+) terminal of a
battery and green wire to the negative (-)
terminal. Wait 5 minutes and blow the hose
with mouth or vacuum pump. If the passage
is blocked, the auto bystarter is normal.
Disconnect the auto bystarter from the
battery. Wait 30 minutes and blow the hose
with mouth or vacuum pump. If air can be Adopter
blown into the hose, the auto bystarter is
normal.
Auto Bystarter
REMOVAL
Remove the set plate screws and set plate.
Remove the auto bystarter from the
carburetor.
Set Plate Screws
Bystarter Valve
AUTO BYSTARTER INSPECTION
Check the auto bystarter valve and needle
for nicks, wear or damage.
If any faulty part is found, replace the auto
bystarter as a set.
Bystarter Needle
INSTALLATION Auto Bystarter
Insert the auto bystarter into the carburetor
body until it bottoms.
Position the set plate into the groove in the
auto bystarter and tighten the screws.
· Be sure to install the auto bystarter and
set plate properly.
· Install the set plate with its bottom face
facing down.
Set Plate Screws
5-5
5. FUEL SYSTEM AGILITY 50
Screws Screws
AIR CUT-OFF VALVE
DISASSEMBLY
Remove the two screws attaching the
throttle cable set plate and the set plate.
Remove the two screws attaching the air
cut-off valve.
Remove the spring and vacuum diaphragm.
Check the vacuum diaphragm for cracks or
damage and check each passage for
clogging.
Throttle Cable Set Plate Air Cut-off Valve Cover
ASSEMBLY
Install the vacuum diaphragm onto the
carburetor.
Install the spring and air cut-off valve cover.
Install the throttle cable set plate and tighten
the two screws.
· Be sure to set the vacuum diaphragm
lip into the groove on the carburetor.
· When installing the air cut-off valve
cover, make sure that the vacuum Diaphragm Spring Cover O-ring
diaphragm is properly installed.
Screws
VACUUM CHAMBER
DISASSEMBLY
Remove the two vacuum chamber cover
screws and the cover.
Vacuum Chamber Cover
Spring Vacuum Diaphragm/Piston
Spring
Remove the spring and vacuum diaphragm/
piston.
5-6
5. FUEL SYSTEM AGILITY 50
Remove the needle holder and jet needle.
Be careful not to damage the vacuum
diaphragm.
Jet Needle
INSPECTION
Inspect the needle for stepped wear.
Inspect the vacuum piston for wear or
damage.
Inspect the diaphragm for deterioration and
tears.
Vacuum Diaphragm
ASSEMBLY Vacuum Diaphragm Vacuum Chamber Cover
Install the vacuum piston/diaphragm in the
carburetor body.
Install the spring and then install the
vacuum chamber cover.
Tighten the two screws.
· Be careful not to damage the diaphragm.
· Hold the vacuum piston while
tightening the vacuum chamber cover.
5-7
5. FUEL SYSTEM AGILITY 50
Screws
FLOAT CHAMBER
DISASSEMBLY
Remove the three float chamber screws and
the float chamber.
Float Chamber
Float Float Valve
Loosen the float pin screw.
Remove the float pin, float and float valve.
Float Pin
Needle Jet Holder Slow Jet
Remove the main jet, needle jet holder,
needle jet, slow jet and pilot screw.
· Be careful not to damage the fuel jets
and pilot screw.
· Before removing, turn the pilot screw
in and carefully count the number of
turns until it seats lightly and then
make a note of this.
· Do not force the pilot screw against its
seat to avoid seat damage.
Pilot Screw Needle Jet Main Jet
Clean the removed fuel jets with detergent
oil and blow them open with compressed
air.
Blow compressed air through all passages
of the carburetor body.
5-8
5. FUEL SYSTEM AGILITY 50
Valve Seat
INSPECTION
Inspect the float valve and valve seat for
damage or clogging.
Inspect the float valve and valve seat
contact area for stepped wear or
contamination.
Worn or contaminated float valve and
valve seat must be replaced because it
will result in float level too high due to
incomplete airtightness.
Needle Jet Holder Slow Jet
ASSEMBLY
Install the slow jet, needle jet, needle jet
holder, main jet and pilot screw.
Return the pilot screw to the original
position as noted during removal.
Standard Opening: 2±1/2 turns
Pilot Screw Needle Jet Main Jet
Float Float Valve
Install the float valve, float and float pin.
Secure the float pin with the screw.
FLOAT LEVEL INSPECTION Float Pin Screw
· Check the operation of the float valve
and float before this inspection.
· Measure the float level by placing the
float level gauge on the float chamber
face parallel with the main jet.
Measure the float level.
Float Level: 17.0mm
This installation sequence is the reverse of
removal.
Float Level Gauge
5-9
5. FUEL SYSTEM AGILITY 50
Screws Diaphragm
ACCELERATING PUMP
DISASSEMBLY
Remove the two accelerating pump cover
screws and accelerating pump cover.
Remove the spring and accelerating pump
diaphragm.
INSPECTION
Inspect the accelerating pump diaphragm
for cracks, damage or deterioration.
Replace if necessary.
Diaphragm
Check each accelerating pump fuel passage
for clogging
Clean and blow them open with compressed
air.
Compressed Air Compressed Air
Install the accelerating pump in the reverse
order of removal.
Be careful not to damage the diaphragm
during installation.
5-10
5. FUEL SYSTEM AGILITY 50
CARBURETOR INSTALLATION Throttle Cable Connecting Tube Band
Tighten the drain screw.
Install the carburetor onto the intake
manifold, aligning the tab on the carburetor
with the cutout in the intake manifold.
Tighten the intake manifold band screw.
Install the air cleaner connecting tube and
tighten the band screw.
Connect the throttle cable to the throttle
wheel on the carburetor.
Tighten the lock nut.
Throttle Cable Lock Nut Adjusting Nut
Connect the fuel tube and vacuum tube to
the carburetor.
Fuel Tube
Connect the auto bystarter wire connector.
Perform the following inspections and
adjustments:
-Throttle grip free play ( 3-3)
-Carburetor idle speed ( 3-5)
Auto Bystarter Wire Connector
5-11
5. FUEL SYSTEM AGILITY 50
PILOT SCREW ADJUSTMENT
* ADJUSTMENT
· The pilot screw is factory pre-set and
no adjustment is necessary. During
carburetor disassembly, note the
number of turns of the pilot screw and
use as a reference when reinstalling it.
· Place the motorcycle on its main stand
on level ground for this operation.
Pilot Screw
A tachometer must be used when adjusting
the engine speed.
Turn the pilot screw clockwise until it seats
lightly and back it out to the specification
given.
Standard Opening: 2±1/2 turns
· The carburetor must be adjusted when
the engine is warm and the auto
bystarter is closed.
· Do not force the pilot screw against its
seat to prevent damage.
Warm up the engine and adjust the throttle
stop screw to obtain the specified idle
speed. Throttle Stop Screw
Idle Speed: 1900 100rpm
Turn the pilot screw in or out slowly to
obtain the highest engine speed.
Slightly accelerate several times to make
sure that the idle speed is within the
specified range.
If the engine misses or runs erratic, repeat
the above steps.
5-12
5. FUEL SYSTEM AGILITY 50
Fuel
Tank
FUEL TANK REMOVE
Remove the net-in box. ( 2-3)
Remove the frame center cover.
Remove the frame body cover. ( 2-3)
Remove the four bolts on the fuel tank, take
the upper seat lock off.
Disconnect the fuel unit wire connector.
Remove the fuel tank.
The installation sequence is the reverse of
removal.
Bolts Seat Lock
Fuel Unit Wite
Connector
FUEL STRAINER REMOVAL
Remove the fuel strainer from the fuel tank.
INSPECTION
Inspect if the fuel strainer is clogged and
clean it with compressed air.
· When removing the fuel strainer, do
not allow flames or sparks near the
working area and drain the residual
gasoline into a container.
Fuel Strainer
INSTALLATION
Install the fuel strainer with its arrow mark
toward the fuel pump.
Arrow Mark
5-13
5. FUEL SYSTEM AGILITY 50
Fuel Unit Wire
FUEL UNIT
REMOVAL
Remove the related parts.
Disconnect the fuel unit wire connector.
Turn the fixed plate on the fuel unit,take the
fuel unit off.
Do not bend the float arm on the fuel
unit,otherwise the figure on the fuel
meter will not correct.
Fuel Tank
INSTALLATION
Inspet if the fuel unit is damaged,or harden.
Assemble the fuel unit in the reverse order
of disassembly.
· Align the groove on the fuel unit with
the angle on the fuel tank.
· Inspect if the fuel tank leaked after
installing and filling the gasoling.
Fuel Unit Align Mark
air cleaner
AIR CLEANER
Loosen the air cleaner connecting tube band
screw.
Disconnect the clinhead cover breather tube
from the air cleaner.
Remove the two bolts and air cleaner case.
bolts
5-14
5. FUEL SYSTEM AGILITY 50
The installation sequence is the reverse of removal.
5-15