Tuning a Bendix carburetor is a job you can complete in just a few minutes. The Bendix carburetor has two adjustment needles on the top of the carburetor. The low-speed adjustment needle is near the mounting bolts in the back, and the high-speed adjustment needle sits just forward of the low-speed needle. The idle stop screw is off to the side of the high-speed needle.
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Start the engine and allow it to warm up for a few minutes. Shut the engine off and turn the low-speed and high-speed adjustment needles clockwise with a screwdriver until they are closed, without over-tightening the needles.
Turn the low-speed adjustment needle counterclockwise 1-3/4 turns. Turn the high-speed adjustment needle 1-1/2 turns counterclockwise.
Start the engine and let it warm up for a few minutes. Turn the low-speed adjustment screw clockwise until the engine starts to stall out, then turn it back counterclockwise one-quarter turn.
Turn the high-speed adjustment needle clockwise one-eighth turn and run the engine at high idle for a few minutes by moving the choke cable forward. Move the choke back to idle speed to check the engine performance.
Repeat the adjustments in Steps 3 and 4, revving the engine and letting it settle into low idle until you reach the optimum performance of the carburetor. Place a tachometer lead wire on the negative ignition coil post and attach the other lead wire to the engine block.
Turn the idle stop screw until it reaches between 2,200 and 2,600 rpm on the tachometer. Readjust the low-speed needle until it is running smoothly.
Remove the tachometer from the engine and turn the motor off.