This vent is just large enough to allow air into the tank, creating enough backpressure to aid in fuel delivery to the carburetor. Surging is also caused by water that got into the fuel. A mower left in a heavy rain or condensation on a hot summer day can choke the engine.Click to see full answer. Likewise, why does my lawn mower engine rev up and down?A carburetor that’s incorrectly adjusted is a common cause of poor engine idling that results in hunting and surging. Fortunately, most lawnmowers have two screws that allow you to adjust the carburetor yourself. Then slowly adjust the screws tighter or looser in turn until the mower runs and idles smoothly.Also, what causes an engine to hunt and surge? If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge. Regarding this, why is my Briggs and Stratton surging? The Surging Test As you know, gas starvation causes an inconsistent flow of fuel which in turn causes erratic running. And, you also know a vacuum leak will cause erratic running, but is a much less common cause. To quickly diagnose which problem you have, follow this simple test.What causes a 4 stroke engine to surge?What would cause a small 4-cycle engine to “surge” rhythmically? Either your gasoline is old/bad or the carburetor is improperly adjusted; that’s a classic symptom of an engine that’s burning a fuel/air mixture that’s just a little too “lean” (not enough fuel for the air).
