Idle Speed and Mixture Adjustment should be set to Lean Best Idle. This does not affect maximum power, but will result in a good idle with maximum fuel economy.
Process
NOTE: Idle speed must be adjusted with engine fully warmed, choke butterfly fully open. Take off air cleaner lid and confirm the choke is fully open before proceeding.
- Adjust curb idle speed. Carburetor Specifications vary, but any stock Datsun engine should idle fine at 750 rpm
- Mixture adjustment. Specs vary, but this will make any stock Datsun run nice:
- Adjust idle to 800 rpm
- turn mixture screw out (anti-clockwise) until engine runs at maximum speed. Readjust idle speed screw to 800 RPM. Repeat until just right.
- turn mixture screw in (clockwise) to lean the mixture down to 750 rpm
- Just learning? To get a 'feel' for this adjustment, turn the screw by half turns clockwise and anticlockwise till you hear the engine speed up and slow down. Then fine turn with 1/4 turns. Do this repeatedly until you are confident of the results