How to get old gas out of a lawn mower

Siphoning Gas

Source: Flikr / bradleyolin

It's always a good idea to drain the gas from your mower at the end of the mowing season or to keep an eye on the fuel level while mowing so that you run out of gas without needing to drain it.

The easiest way to do this, of course, is to just open the throttle wide open and let the engine run until it's out of gas. Often, though, people just simply forget this last step, and that's where the trouble starts. Gas that's been in the mower for more than a couple of months can “go bad," with sediment, varnish-like contaminants, and condensation that can make it difficult to even start the mower again when the time comes. If you find yourself in this situation, here are some steps you can take to get old gas out of a lawn mower.

Vehicle System
Othermotive
Skill Level
Beginner

This is a good project for new DIYers

Time to Complete
30 to 45 minutes
    How to get old gas out of a lawn mower
  1. Spread a tarp under the mower (it's best to do this outside, where the ventilation will be better). Make sure you take safety precautions, including using safety glasses and gloves, and have some kitty litter handy as a quick-dry for spills.

  2. Remove the gas cap and use an old rag to wipe out the inside of the filler.

  3. Run a siphon hose from the fuel tank to a gas can on the ground and squeeze the bulb enough times to create a vacuum that will start draining gas from the fuel tank to the can.

  4. Drain as much as you can from the tank with the siphon hose.

  5. Next, get a look at the carburetor and see if it has a drainage bolt on the bottom of the float tank.

  6. If possible, remove this drainage bolt and let the fuel run out of the float tank. Then, remove the entire carburetor.

  7.  Spray the bore, choke, and any other accessible parts of the carburetor with aerosol carburetor cleaner and reinstall it on the engine.

  8. Reassemble all parts and start the engine. You may need to spray starting fluid in the carburetor's bore to get it running again. With any luck, you should be ready to go again for another season of mowing and yard work.

  9. Pro Tip

    Remember to drain the fuel at the end of the season, and you'll save yourself a lot of trouble for next year!

Last updated June 6, 2018

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