2SE Carburetor

Fig 70 - Idle Speed Drop Chart:

Fig 72 - Idle Mixture Plug Removal:

Idle mixture adjustment should only be performed if the mixture adjusting screw has been replaced or removed during carburetor overhaul. Mixture adjustments should not be made as a normal service adjustment.


The mixture adjusting screw is recessed into the throttle body an sealed with a hardened steel plug. Do not remove plug and adjust idle mixture unless performing carburetor overhaul, replacing the throttle body, or high CO emissions have been detected using proper test equipment.

1. Remove carburetor from engine and drain fuel from float bowl into a suitable container.
2. Mount carburetor, manifold side up, in suitable holding fixture.
3. Using a punch between two locator points on throttle body manifold side, Fig. 72, breakout throttle body to gain access to steel plug.
4. Drive out steel plug covering mixture adjusting screw.

NOTE: Hardened plug will shatter rather than remain intact. It is not necessary to remove plug completely. Remove loose pieces to allow use of mixture adjusting tool.

5. Turn mixture adjusting screw in (clockwise) until lightly seated, then back screw out 3 turns.
6. Reinstall carburetor and install tachometer on engine. Start engine and warm to operating temperature, then adjust idle speed to specifications.
7. Turn mixture adjusting screw clockwise (leaner) until loss of RPM is indicated on tachometer.
8. Turn mixture adjusting screw counterclockwise (richer) until maximum RPM is obtained. Do not turn screw farther than point at which highest RPM is first obtained.

NOTE: Engine speed should increase an amount corresponding approximately to the "lean drop specification," Fig. 70.

9. Turn mixture adjusting screw clockwise, in small increments, until specified RPM drop, Fig, 70, is obtained.
10. If final engine speed differs more than 30 RPM from originally set curb idle speed, reset idle speed to specifications and repeat steps 5-9.
11. Set idle speed to specifications and install air cleaner.