Briggs 18hp Engine Idle help

[stargate4]

Carburetor flooding??

Greetings everyone, Lewis here again from Monterey, TN. After putting new gas line, new fuel pump, cleaning carburetor and taking the gas tank out and having it cleaned I still had problems with the 18 hp B&S idling. I ended up getting a new Nikki carburetor and installing it. Now it idles really good but another problem has cropped up. It backfires out the exhaust and up through the carburetor. I suspect the mixture is too rich, building up gas in the muffler causing it to backfire. Also, when I open the throttle pretty quickly you can see droplets of gasoling being blown out the top of the carburetor and there is a considerable lag time in the throttle. I haven't found any adjustments on the carburetor to lean down the mixture and since it is idling good I hesitate to mess with the idle mixture screw. I was wondering if someone else has had the same problems and how they fixed them. Any help would be appreciated... It seems like this thing is slowly devouring money and I am getting nothing in return except more work on it. Thanks for any help/suggestions.... Lewis

[Roger S]

Those are lean symtoms. Richen the mixture screw, counter clockwise and see what happens. There are other things that might be the problem, like valve adjustment or vacuum leaks on the intake system, spark plugs.. but don't be afraid to turn the mixture screw.

The fastest idle speed you get from adjusting the mixture screw, will be too lean for good driveability. Turn it out a 1/4 turn from there. Or until the acceleration stumble goes away.