I've bought a strimmer for a few quids and I've just managed to start it.

However, the air filter is missing. The part is discontinued — or likely to cost me more than the strimmer itself in case I manage to find it in a remote part of the Internet.

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I'm missing part 17 in the picture above — similar to this picture:

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I don't intend to have a very heavy use of the streamer (say, a few times per year, for 15-mins max). But I understand a bit of grass entering the carburetor won't do good.
So what could I use as a poor man's air filter?

I was thinking of either:

  • fill part #12 with cotton wool (the center hole is the air inlet), and keep it in place with some electric tape,
  • wrap a coffee filter around part #12.
  • I reckon this question is not quite “motor vehicle” oriented — but the audience might be more appropriate to answer than DIY.stackexchange.
    – ebosi
    Jun 26, 2023 at 16:24
  • 2
    This is a perfectly valid question here, small engines are on-topic.
    – juhist
    Jun 26, 2023 at 16:32
  • 1
    As a hack a fine-mesh stocking pulled over part 12 might be better then nothing. Jun 26, 2023 at 16:45
  • @juhist is correct ... your trimmer has an internal combustion engine ... questions about it are fair game. Jun 26, 2023 at 16:52

1 Answer 1


I would actually suggest you to buy a foam air filter element that is big enough. Usually they are sold for certain specific types of engines, like certain lawnmowers or certain generators. However, you probably are able to buy an air filter element big enough. Then cut it with scissors to very slightly larger than the proper size and compress it in place. Use duct tape to hold it in place, and seal the sides. You probably are missing the air filter cover too, but you don't actually need it. It's perfectly possible to use an air filter without the cover provided that you have some way of holding it in place (in this case, duct tape).

Foam air filters should be gently soaked in oil and compressed inside paper towels to remove excess oil. So there's a danger of getting your hands or clothes oily if you touch the air filter. Usually in real equipment the air filter cover prevents that from happening. But as long as you don't do that, it works well.

Then occasionally you need to clean the air filter in liquid water and detergent, dry it, re-oil it, and remove excess oil again with the paper towel trick. So you need to remove the duct tape occasionally.

Coffee filters don't work. Air filters made out of paper have surface area far larger than the area of the filter itself, because the filter paper is in a steep "V" shape. With coffee filter, this is not possible.

Edit: As for the oil that should be used, any engine oil works. Presumably that's a 2-stroke engine. So you are mixing 2-stroke oil in your gasoline, right? Because if you aren't, the engine will be destroyed in a very short duration of time. The very same 2-stroke oil is probably good for oiling the foam air filter element. There is no special air filter oil, they are oiled with just regular engine oil, either the 4-stroke oil that goes into oil pan or the 2-stroke oil that's mixed with gasoline. Any food/cooking oil will have too short shelf-life and will ruin the air filter element very fast. Any fuel will be flammable, creating a fire hazard.

  • 1
    And if the OP was feeling completely froggy, a person could fairly easily 3d print a cover for it without too much of a hassle. Jun 26, 2023 at 16:55
  • thanks! What oil should I use? Oil as in petrol, engine oil, or cooking oil?
    – ebosi
    Jun 26, 2023 at 20:36
  • 1
    Mineral (engine) oil is probably best as vegetable oil is likely to go rancid. Don't use petrol as this will quickly evaporate.
    – Frog
    Jun 27, 2023 at 1:34
  • Paper air filters used for other things (vacuum cleaners, cooker hoods) may be cheap and adaptable but because of their folded nature they'd be far harder to cut down than a foam filter. You might want a spacer under a foam filter so it doesn't rest on the base of the housing - you'll get better airflow if air can be pulled through the whole area rather than just the bit nearest the hole. And I'd probably DIY a better cover than just duct tape, using things like a plastic lid with holes drilled in it, and a hose clip, or cable ties to holes drilled in the tabs the real cover should clip to
    – Chris H
    Jun 27, 2023 at 14:15
  • 1
    @ebosi I edited the answer to include which kind of oil should be used.
    – juhist
    Jun 27, 2023 at 16:06

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