Note

Low speed mixture screw (12) is turned clockwise, or in, to make leaner mixture, and counterclockwise, or out, to make mixture richer. Screw is held in position by a spring (13).

Adjust throttle stop screw (10) to make engine idle at desired speed with throttle closed. Turning screw clockwise opens throttle plate for faster idle. Never set idle adjustment to slowest possible speed. An extremely slow idle causes bearing wear, oil consumption, and slow speed accelerating difficulties. Recommended idle speed is 900 rpm.

Make final readjustment on low speed mixture screw (12) after engine is warm. First turn screw in, then out, to see if engine picks up speed or runs more smoothly. Starting and all around performance will be better with mixture adjustment set slightly richer than leaner. If necessary, make further adjustment on throttle stop screw (10) to obtain correct engine idling speed.

During high speed operation, fuel is metered by a main jet (26) which has no adjustment. Operating conditions, such as high altitudes or hard service, may require a different size main jet other than the standard. The following main jet sizes are available:

Main Jet Size

The amount of fuel injected by the accelerating pump is adjusted by means of the rocker arm adjusting screw (3). Factory adjustment is 6 mm (approximately 1/4 in.) between end of screw and stop. Back screw out for more fuel volume; in for less. The rocker arm spring (45) controls stroke duration and is adjustable by means of three locating notches in the accelerator pump rocker arm (44). Center notch is standard adjustment.

DISASSEMBLING (Figure 3-77)

Turn off gas tank valve and disconnect fuel line at carburetor. Disconnect throttle wire and choke wire from their respective operating levers. Detach carburetor from engine by removing nuts and washers from mounting studs. Note position of gaskets.

Disassemble accelerating pump parts as follows: Remove accelerating pump housing (33) by removing three sets of screws and washers (34 and 35). Remove spring (32), diaphragm (31) and two O-rings (30), taking care when lifting off housing (33) to catch spring (32). Also, be careful not to damage housing mounting surface to prevent fuel leakage when reassembled.

Disassemble float chamber as follows. Detach float chamber (29) from body by removing three sets of screws and washers (34). Remove screw (6) which retains float pin (5). Remove float pin (5) and remove float (23). Slip off fuel valve (21) from metal clip on float. If needed, remove clip (22) from fuel valve (21). Take care not to damage rubber needle portion of fuel valve (21). Also be careful not to damage pump nozzle and overfloat pipe which are built into the float chamber. Remove O-ring (28) from slot in float chamber wall.

The removal of the float chamber will allow pump rod (7] and boot (8) to be removed next.

Disassemble carburetor body as follows. Pull plug (27) out of tube above slow jet (25). Unscrew slow jet (25) and main jet (26). Tip body and let main nozzle (24) slide out of main tube.

Remove O-ring (20) from slot in body mounting flange. Unscrew and remove nut (1 9) along with washer (18). This will free throttle lever (17) and spring (16) so they can be pullec off throttle shaft.

Unscrew throttle stop screw (10) and low speed mixture screw (12) along with associated springs (11) and (13), respectively.

As required, remove brackets (2) and (15) by removing screws and washers (1) and (14), respectively.

The throttle valve assembly and choke valve assembly (shaft, valve, plate and associated parts) usually are not disassembled. These parts are matched to the individual carburetor during manufacture. In both cases, screws securing plates to shafts have peened ends, the threads of which would be destroyed if screws are removed. In the case of throttle assembly, the position of bypass hole was positioned precisely to match lip of valve and would be changed if taken apart and reassembled. If problems arise involving these assemblies, the complete carburetor is usually replaced.

This completes disassembly of carburetor. Clean anc inspect before reassembling.

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