Briggs Opposed Twin 20hp Surging

davbell22602

davbell22602

Lawn Addict
Briggs 20hp vertical shaft

461707
0143e1
9904285B

Rebuild it carb and cooked it in ultrasonic cleaner for one hour with heat. Still surges on idle and top speed. Carb just has ide speed screw. Carb doesnt have a removable seat either. This is the 4 screw fuel pump carb setup.
 
Give it a little choke and see if that clears it up, IF so, running to lean. IF it makes it run worse, running too rich. there were about 3 different gaskets for between the carb and the air cleaner box for this engine. There is a small vent hole in the mating surface which is different with different carbs, hence the different gaskets. Check that the gasket is not blocking the vent hole. Run without air filter box as possible test.

Walt Conner
 
Tinkerer200 said:
Give it a little choke and see if that clears it up, IF so, running to lean. IF it makes it run worse, running too rich. there were about 3 different gaskets for between the carb and the air cleaner box for this engine. There is a small vent hole in the mating surface which is different with different carbs, hence the different gaskets. Check that the gasket is not blocking the vent hole. Run without air filter box as possible test.

Walt Conner
Click to expand...
Still surges with the air box removed. This carb has no adjustment except for the idle.
 
You didn't say what, if any, affect adding choke had. Also, you didn't say if you visually checked if the vent hole in gasket lined up with carb vent hole.
Walt Conner
 
Surging is usually a lean running problem, but can occasionally be caused by the governor system, hold your finger on the throttle shaft, so it stays in position, or one engine speed so to speak, if dies out, you have a fuel delivery issue.
 
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