What causes a lawnmower engine to rev up and down?

What causes lawn mower engine surging?

Problems in the Fuel System

The cap on your mower’s gas tank is vented with a small hole. … 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. Empty the gas tank, properly dispose of the old fuel and try a fresh batch of gasoline.

Why does my lawn mower keep bogging down?

The most common reason why lawn mowers bog down, especially mulching mowers, is grass clippings sticking to the underside of the deck. If your mower packs in too many clippings, there’s not enough room for the clippings to cycle and the blade to keep turning. Fixing this is easy enough, it’s just a messy job.

Can spark plugs cause surging?

3. Surging and Lagging. Another good indication that your spark plugs are dirty or worn is if your vehicle experiences surges of speed, resulting in a jerking acceleration. These surges occur because your spark plugs are not igniting the fuel in your engine at the proper rate, resulting in an uneven speed.

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Why does my lawn mower rattle?

One of the most commonly experienced noises from a lawnmower is a loud rattling sound resulting from a loose blade assembly. If the blade assembly is loose, it will move around during startup, and it will keep on rattling as the lawnmower runs.

What is the cause of engine surging?

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.

What causes a carbureted engine to surge?

Incorrect fuel mixture adjustments and engine idling capabilities can be upset by fuel mixture adjustments and fuel vapor recovery system malfunction. The fuel system cleaner added to the fuel tank can open blocked passages in the fuel system that could be causing the surge.

What is engine hunting and surging?

The most common cause of engines ‘hunting or surging’ is stale fuel evaporating, leaving residue on the main jet or dirty fuel causing partial blockage of the jet. If the motor runs smoothly on partial choke, this usually indicates main jet restriction.

Why does lawn mower engine pulsate?

The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities: Bad gas. Bad spark plug. Dirty / faulty carburetor.

What causes mower to bog down when blades engaged?

A mower that bogs down when the blades are engaged is a symptom of bigger problems with your mower. You may not have a large enough mower if your grass is exceptionally thick or tall. Mechanical issues with the mower deck, drive train, or throttle assembly may also be to blame.

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Can a bad battery cause a lawn mower to stall?

Check that all the safety switches are working correctly, it is possible the seat switch is bad or loose plug/ bad wire. Also if battery weak or charging system weak/faulty the clutch will stall out engine, charge battery up with charger and try.