Removing
Disconnect the negative battery terminal, air cleaner hoses and remove the air box.
Note the location of the dowel marks on the bimetal spring housing for ease of installation and. if necessary, make additional marks, then unscrew the three screws and remove the bimetal spring housing. Move it to the side, being careful not to pull on the hoses or wiring.
Remove the three screws securing the choke body to the carburetor body, remove the throttle body, being careful not to bend the actuator stem.
Remove, if necessary, the bimetal spring housing for replacement, while operating as follows, otherwise omit the following three points.
Note the location of the automatic air damper cooling hoses for easier installation, then disconnect the hoses. There is a possibility of coolant leakage, therefore it is necessary to clamp the hoses or hang them upside down.
Disconnect the wiring from the air damper heater and pull out the bimetal spring housing.
The cooling jacket can be removed from the bimetal spring housing by unscrewing the central bolt. Remove the o-rings from under the bolt head and from the rim of the cooling casing.
Installation
Begin installation by placing the choke assembly in the carburetor body, making sure its lever engages with the operating rod. Tighten the three screws.
Check and, if necessary, adjust the choke gap and the position of the fast idle adjustment cam as follows.
Connect the bimetal spring to the choke lever, install its body and choke body in the position noted during removal, then tighten the screws.
If required, install the cooling shroud to the spring housing, new o-rings, and connect the cooling hoses and choke heater wiring.
Installation is carried out in the reverse order of removal, taking into account the following.
If the cooling hoses were disconnected, check the coolant level.
Check and, if necessary, adjust the fast idle speed as described in this section.
Air damper gap adjustment
After removing the bimetallic spring housing, the operation procedure is as follows.
Press the choke lever fully clockwise and hold it in this position with a rubber band.
Press the throttle lever to its fully open position and measure the air damper gap between the bottom side of the damper and the secondary chamber diffuser wall. It must meet the specification.
Adjust, if necessary, the air damper gap by bending the segment (2). Figure 4.31. If the gap is too small. increase clearance (IN) with a screwdriver. If the clearance is too large, the clearance must be reduced (IN) using pliers.
If no further adjustment is required, reinstall the bimetal spring housing as previously indicated.
Fast idle adjustment cam location
After removing the bimetal spring housing and setting the air damper gap ("A" in Figure 4.32.), continue as below.
Open the throttle, then close the choke by lightly pushing the choke lever with your finger. Close throttle.
Check if the fast idle speed adjustment screw rests against the highest step of the cam.
If adjustment is required, first check that the choke return spring is correctly installed, then adjust with the lever (2).
Install the bimetal spring housing as described earlier.
Fast idle speed adjustment
Note: An accurate tachometer and an exhaust gas analyzer are required for adjustment.
Check mixture quality and idle speed. The idle speed must be exactly within specification before checking or adjusting the fast idle speed.
The engine must be at normal operating temperature and the tachometer connected according to the manufacturer's instructions. Then the work is done in the following order.
Set the adjusting screw to the highest step of the cam.
Start the engine without touching the accelerator pedal and check that the idle speed is correct. If adjustment is needed, stop the engine and follow the steps below.
Remove the special safety cap from the fast idle adjustment screw - (please observe national laws).
Check if the adjusting screw is set on the second high step of the fast idle adjustment cam, then start the engine without depressing the accelerator pedal again.
Turn the adjusting screw with a screwdriver until the fast idle speed is set to specification.
If the cooling fan turns on during these operations, stop the adjustment and continue operation only after the fan stops.
After completing the adjustment, turn off the engine and disconnect the tachometer.
Install a new safety cap on the fast idle adjustment screw.
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