How to Adjust Carburetor Settings on a Small Gas Engine

April 10, 2012



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Is your lawn mower having trouble starting or does if easily stall?

We will you help you find the solution to the problem and help you understand the workings of your small gas engine.

How does the small gas engine on your lawnmower (and other outdoor power equipment) start?

The carburetor is the first step in this process – it mixes the fuel and the air, then sends the mixture to the spark plugs for combustion. The choke plate is the part that regulates the amount of air that is mixed with the fuel, ensuring that the proportions are right. While the choke plate settings are completed at the factory where your lawn mower is made, dirty air or fuel can damage the plate and call for adjustment.

If your lawn mower (or other outdoor power equipment) has difficulty starting or easily stalls, these are the steps you need to take to adjust the choke plate and make sure that your lawn mower runs trouble free this grass cutting season:

  • Remove the blade off your lawn mower.
  • Remove lawn mower air filter. Depending on your engine model, the air filter can be located in a number of places, so look for a small box (or cylinder) near the carburetor. The box is held closed with a screw, so unscrew the cover and the air filter should slide out easily. Inspect the filter. If dirty or coated with grass or garden debris, replace the filter with a new one, then screw the cover back into place.
  • Start the engine, then turn the choke off letting the engine idle for a short while. This allows any dirt and debris that may have accumulated in the fuel system to be cleared away. Locate the three adjustment screws on the carburetor, usually to be found near the bottom of the carburetor, near the fuel line.
  • Put the engine into gear, then place the screwdriver into the slot of the main fuel mix screw. Rotate the screw counterclockwise until the engine begins to throb – evidence that there is too much fuel in the mixture. Slowly rotate the screw clockwise until the engine starts to stall – evidence that the fuel mixture is too low. For the perfect mixture of fuel and air, reset the screw between these two points.
  • Rotate the screw and adjust to the point until the engine runs smoothly.
  • Replace the blade.
Tune up kits for every small engine

Tune up kits for every small engine

Don’t forget to tune up your lawn mower engine this spring. Everything you need – small engine parts, instructional videos, repair help and more, can be found at this excellent outdoor power equipment resource website.
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