Tecumseh and Walbro Carburetors Final Adjustment

Start the engine and allow it to warm up to normal operating temperature (3 - 5 minutes). Set the speed control to the HIGH or FAST position. From the recommended preset position, turn the main mixture adjustment screw in (clockwise) slowly until the engine begins to run erratic (lean). Note the position of the screw. Now, turn the screw out (counterclockwise) until the engine begins to run erratic (rich). Turn the screw in (clockwise) midway between these two positions. This will be the best setting. (Fig. 21, 22 & 23).

Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure used to adjust the main mixture adjustment screw.

If further adjustment is required, the main adjustment should be made under a loaded condition.

If the engine stops or hesitates while engaging the load (lean), turn the main mixture adjusting screw out
(counterclockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is
corrected.

If the engine smokes excessively (rich), turn the main adjusting screw in (clockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is corrected.

After the main mixture screw is set, move the speed control to the IDLE or SLOW position. If the engine does not idle smoothly, turn the idle mixture screw 1/8 turn either in (clockwise) or out (counterclockwise) until engine idles smoothly.

Recheck the high and low R.P.M. setting and adjust as necessary.

Tecumseh and Walbro Carburetors Preset Adjustment

Turn both the main and idle mixture adjusting screws in (clockwise) until finger tight.
Now back the mixture screws out (counterclockwise) to obtain the pre-set figure in the chart shown at bellow.