Provides a richer mixture for cold starts. Verified Tuning Specifications
Turn the screw in or out by 1/4-turn increments until you find the highest, smoothest idle speed.
Spray carburetor cleaner around the rubber intake manifold while the engine runs. If the RPM changes, replace the leaking manifold or O-ring. If no leak exists, back the pilot mixture screw out an additional 1/4 turn.
Use JIS (Japanese Industrial Standard) Phillips screwdrivers to avoid stripping the soft brass or aluminum screws common on these units. Step-by-Step Tuning Order
This points to the float system. The cause is often a worn-out float bowl gasket , which becomes compressed and hard over time. More severely, a sticking float needle or incorrect float height can cause fuel to overflow from the bowl's drain tube.
If you must turn the screw more than 3 turns out, the pilot jet is likely too small. If bottoming the screw doesn't kill the engine, the jet is too large. Mid-Range (Jet Needle)