How to Adjust the Carburetor Mixture Ratio?
2 Answers
Check the tightness of the connections related to the carburetor to ensure normal air intake without any air leaks or intake blockages. Turn the carburetor mixture screw clockwise all the way, then turn it counterclockwise 1.5 turns. Start the engine and let it warm up for 10 minutes to reach normal operating temperature. Adjust the carburetor idle speed screw so that the engine runs at the lowest possible speed without stalling. Repeatedly adjust the carburetor mixture screw left and right to achieve the highest engine speed.
I've tuned quite a few carburetors myself, and the key to this job is patience. First, start the car and let it warm up for ten minutes—the engine needs to reach normal temperature for proper tuning. Locate the small spring-loaded screw on the side of the carburetor—that's the air-fuel mixture screw—and turn it slowly with a flathead screwdriver. Turning it clockwise enriches the mixture, while counterclockwise leans it out. Listen to the engine as you adjust; the moment the RPM suddenly spikes, stop—that's the sweet spot. Then, adjust the larger idle screw nearby to bring the RPM back down to around 1500. If the RPM starts jumping around, you'll have to start over. Test-driving is crucial after tuning—take it for a spin to check if acceleration is smooth and whether black smoke comes out of the exhaust. The screw directions may vary by carburetor brand, so it's best to check the manual beforehand. If tuned right, you can squeeze out dozens more kilometers per tank.
