How to Adjust an Overly Rich Carburetor Mixture?
2 Answers
First, check the tightness of all connections related to the carburetor. Turn the carburetor mixture screw clockwise until it stops. Start the engine and let it warm up for 10 minutes. Adjust the carburetor mixture screw back and forth until the engine reaches its highest RPM. Observe whether the engine accelerates and decelerates smoothly.
I remember when I drove the old Jeep, I also encountered the issue of the carburetor mixture being too rich. It was spewing black smoke and guzzling fuel. When adjusting, you had to first locate the idle mixture screw, usually turning it counterclockwise slowly to let more air in and less fuel, turning just a quarter turn at a time before stopping to test drive. A too-high float chamber fuel level was also a common problem, requiring disassembly to adjust the float height—using calipers for measurement was the safest bet. A clogged air filter could also cause the mixture to be too rich; it was handy to take it off and tap out the dust or simply replace it with a new one. If the choke valve was stuck in the closed position, it was even more troublesome, requiring careful cleaning with carburetor cleaner. Honestly, tuning this thing really tested your patience, with the RPMs going up and down, requiring repeated adjustments until the exhaust didn’t stink or emit black smoke, which meant it was properly tuned.
