9. Fuel System
9.5 Removing and Installing the Carburetor
– Remove the shroud, b 6.2 – Remove the filter housing, b 9.4 – Open the fuel tank cap and drain
the fuel tank, b 1.1
Disconnect the fuel hoses only when the tank cap is open.
Always install new fuel hoses.
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: Pull the fuel hoses (1) out of the guides (arrows).
: Pull the throttle cable (1) and wiring harness (2) out of the guides (arrows).
– Press down the throttle lever until the nipple (arrow) projects.
: Take the throttle cable (1) out of the pin (2).
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: Pull the fuel hose (1) off the nipple (arrow).
: Remove the carburetor (1).
: Pull the fuel hose (1) off the nipple (arrow).
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: Remove the gasket (1).
: Check and clean the sealing faces (arrows) on the spacer flange and carburetor, b 13 Always replace components with damaged sealing faces.
Installing
: Fit the gasket (1).
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: Fit the new fuel suction hose (1) onto the carburetor's
nipple (arrow)
– the fuel suction hose must be pushed fully home.
– Push the carburetor into position.
: Fit the new fuel hose (1) onto the carburetor's nipple (arrow) – the fuel hose must be pushed fully home.
Take care not to damage the new fuel hoses.
– Reassemble all other parts in the reverse sequence.
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9.5.1 Leakage Test
In the case of problems with the carburetor or fuel supply system, also check and clean or replace the tank vent, b 9.10
The carburetor can be tested for leaks with the pump
0000 850 1300.
Install new fuel hoses after completing the test.
Take care not to damage the new fuel hoses.
– Remove the carburetor, b 9.5
: Push the hose (1) 1110 141 8600 on to the nipple (2)
0000 855 9200.
: Push the hose with nipple onto the carburetor’s fuel
nipple (arrow).
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– Connect hose of pump 0000 850 1300 to the nipple.
: Push the ring (1) to the right and pump air into the carburetor until the pressure gauge (2) indicates a pressure of about 0.8
bar (80 kPa).
If this pressure remains constant, the carburetor is airtight. However, if it drops, there are three possible causes:
1 The inlet needle is not sealing (foreign matter in valve seat, sealing cone of inlet needleis damaged or inlet control lever is sticking). Remove to clean, b 9.6.2
2 Metering diaphragm damaged, replace if necessary, b 9.6.1 3 Pump diaphragm damaged,
replaceif necessary, b 9.6.4 – After completing the test, push
the ring (1) to the left to vent the system and then pull the hose off the carburetor's nipple.
– Install the carburetor, b 9.5 – Reassemble all other parts in the
reverse sequence.
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9.6 Servicing the Carburetor9.6.1 Metering Diaphragm
– Remove the carburetor, b 9.5 : Take out the screws (arrows).
– Remove the end cover (1).
If the gasket and diaphragm are stuck to the carburetor, remove them very carefully.
: Carefully separate the metering diaphragm (1) and gasket (2).
The diaphragm material is
subjected to continuous alternating stresses and eventually shows signs of fatigue. i.e. the diaphragm distorts and swells and has to be replaced.
– Note installed positions of metering diaphragm (1) and gasket (2).
: Line up the gasket (2) and metering diaphragm (1) with the holes (arrows).
: Position the end cover (1) so that the hose barb (2) is on the same side as the adjusting screws.
– Fit the end cover.
: Fit the screws (arrows).
– Check position of metering diaphragm and gasket, then tighten down the screws firmly in a crosswise pattern.
– Reassemble all other parts in the reverse sequence.
9.6.2 Inlet Needle
– Remove the metering diaphragm, b 9.6.1 : Take out the screw (arrow).
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: Remove the inlet control lever (1) with spindle (2) out of the inlet needle’s groove.
The small spring under the inlet control lever may pop out.
: Remove the inlet needle (1).
: Remove the spring (2).
: If there is an annular indentation (arrow) on the sealing cone of the inlet needle, fit a new inlet needle.
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: Fit the inlet needle (1).
: Fit the spring (2) in the bore.
: Position the inlet control lever (1) with spindle (2) on the spring’s seat (arrow) first, then slide the inlet control lever’s clevis into the groove in the inlet needle (3).
Make sure the spring locates on the control lever’s nipple (arrow).
– Press the inlet control lever down and secure it with the screw.
– Check that the inlet control lever moves freely.
– Install the metering diaphragm, b 9.6.1
– Reassemble all other parts in the reverse sequence.
9.6.3 Fixed Jet
– Remove the metering diaphragm, b 9.6.1
: Unscrew the fixed jet (1) with a suitable screwdriver.
– Reassemble in the reverse sequence.
9.6.4 Pump Diaphragm
– Remove the carburetor, b 9.5 : Take out the screw (arrow).
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: Carefully remove the end cover (1).
: Carefully remove the gasket with pump diaphragm from the end cover.
: Carefully separate the pump diaphragm (1) and gasket (2).
The diaphragm material is
subjected to continuous alternating stresses and eventually shows
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: Check fuel strainer for contamination and damage.
Clean or replace if necessary.
– Reassemble in the reverse sequence.
Installing
: Fit the gasket (1) so that the contours (arrows) match and it is held in position by the pegs (2).
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: Fit the diaphragm on the gasket (1) so that the
contours (arrows) match and it is held in position by the pegs (2).
– Position the end cover (1) so that the stop screw (arrow) points in the direction of the adjusting screws.
: Turn lever (2) on throttle shaft a little and place the end cover (1) against the carburetor body from below so that the gasket and pump diaphragm remain in position on the end cover.
– Move the end cover (1) a little until its pegs engage the holes in the carburetor body.
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– Check that diaphragm and gasket are properly seated.
: Insert and tighten down the screw (1) firmly.
– Reassemble all other parts in the reverse sequence.
9.6.5 Throttle Lever
– Remove the carburetor, b 9.5
: Take out the screw (arrow).
– Pull off the throttle lever (1).
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Installing
: Hold the throttle lever (1) so that the slotted pin (arrow) faces up and the flat sided hole is in line with the throttle shaft (2).
– Push the throttle lever (1) onto the end of the throttle
shaft (arrow).
: Insert and tighten down the screw (2) firmly.
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– Check operation.
: Rotate the choke shaft. The lever (1) must engage the throttle lever (arrow).
– Reassemble all other parts in the reverse sequence.
9.6.6 Rotary Knob
: Take out the screw (arrow).
– Pull off the rotary knob (1).
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Installing
– Turn the rotary knob (1) until it is seated in the guide sleeve (2).
– Fit the spring (1) on the choke shaft.
– Position the rotary knob (2) so that the holes (arrows) are in alignment.
: Push the rotary knob (2) onto the choke shaft until it engages, and hold it in that position.
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: Insert screw (arrow) and tighten it down firmly.
– Check operation.
– Press the rotary knob = the knob can be rotated 2 notches clockwise.
– Turn the rotary knob back to the stop = it springs back to its original position
– – knob is locked.
– Reassemble all other parts in the reverse sequence.
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9.6.7 Adjusting Screws
There are three adjusting screws on the carburetor:
H = high speed screw (1) L = low speed screw (2) LA = idle speed screw (3)
If the carburetor cannot be adjusted properly, the problem may be the adjusting screws.
The high speed screw (H) has a limiter cap, which has to be removed before the screw is removed.
Always install a new limiter cap.
– Remove the shroud, b 4.4 It is not necessary to remove the carburetor to remove and install the adjusting screws. For the sake of clarity, however, the illustrations show the carburetor removed from the machine.
– See also carburetor troubleshooting, b 3.4
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Low Speed Screw (L)
: Take out the low speed screw L (1).
: Inspect the tip (arrow) for damage or wear and replace the low speed screw (L) if necessary.
Installing
– Carefully turn the low speed screw (L) clockwise as far as stop.
– Check the high speed screw (H) and replace it if necessary.
– Carry out the basic setting, b 9.7.1
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High Speed Screw (H)
: Use puller 5910 890 4501 to pry the limiter cap (1) off the high speed screw (H).
Do not re-install a used cap – always fit a new cap.
: Take out the high speed screw H (1).
: Inspect the tip (arrow) for damage or wear and replace the screw (H) if necessary.
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Installing
: Carefully turn the high speed screw H (1) clockwise as far as stop.
– Carry out the basic setting, b 9.7.1
9.7 Adjusting the Carburetor