Adjusting Idle Fuel Mixture
Short answer: The idle mixture screws are the only control for idle fuel mixture — the main jets meter everything above idle, and changing jets won’t affect the idle. Adjust the screws for the smoothest idle, then lean slightly.
A common trap: an unburned-fuel smell that seems “too rich” is often actually too lean — the resulting misfire dumps raw fuel out the exhaust. Check for vacuum leaks, correct timing, and dwell (if you have points). Also remember a high-mileage engine can smell of unburned fuel simply from worn cylinder sealing, even when it runs well.
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Content last modified: June 13, 2026 at 10:06 am
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