Mothballing Small Engines for Storage.

mothballing small engines

Over the years, I have learned about mothballing small engines the hard way.  Years ago I failed to mothball engines correctly, just shutting them down and forgetting about them.  Several years later I attempted to start them and ended up taking them to the repair shop. It was not a cheap experience.

Since then if I am going to let an engine sit for any length of time I am careful to mothball it.  My limit is about 90 days, anything over that and I mothball.  Since I have been doing that, I have not had any further problems.

I mothball two and four stroke engines slightly differently.  First with both types, I clean the engine prior to getting it ready for storage.  I make sure there is no debris on the exterior that is going to collect moisture or cause corrosion.

Mothball Small Engines, 2 stroke (requires oil & gas mix)

  1. Start up the unit and run the engine until it stops from running out of gas. If the gas tank is full, you may want to drain most of the gas out prior to running it out of fuel.  After the engine stops, pull the starter cord a couple of times until the engine no longer sputters from gas remnants left in the fuel system.
  1. The next step is to remove the spark plug, squirt a small amount of lubricant (I use Marvel Mystery Oil) into the spark plug hole, and pull the starter cord a few times. This will lubricate the engine’s cylinder parts. Reinstall the spark plug. Your equipment is now ready for storage.
  1. Store it in an area in which it stays clean and dry. Exposure to moisture can cause damage.
  1. When you take it out of storage, fill it with the correct fuel mixture and it should start right away.
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Mothballing Small Engines 4 Stroke (requires straight gasoline only – NO oil mix)

  1. Start the engine and let it run until it stops from lack of fuel
  1. Remove any remaining fuel from the carburetor. This is done several ways depending on the manufacturer of your equipment. First you must find your carburetor’s fuel bowl by following the fuel line from your fuel tank to the engine.
  • If your fuel bowl has a drain on the bottom, loosen the drain bolt or valve and drain out the remaining fuel.
  • If the fuel bowl has a big bolt in the middle, break the bolt loose and drain the fuel. Then retighten the bolt.
  • If your fuel bowl does not have a drain or bolt in the middle of it, you will have to remove the fuel bowl. This can be done by removing the two screws at either corners of the fuel bowl where it bolts to the carburetor. Remove the bowl and dump out any remaining fuel. Then replace the bowl onto the carburetor.
  1. Remove the spark plug and squirt a small amount of lubricant into each cylinder. Pull the starter cord a few times to lubricate the cylinders. Replace the spark plugs.
  1. Place in a clean dry area to protect it from moisture.
mothballing small engines
This is the lubricant I use.

It takes a bit of work to mothball small engines in this manner, but you can count on them starting when you really need them.


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4 thoughts on “Mothballing Small Engines for Storage.”

  1. Veteran Who Is Preparing

    Thanks for posting this. It goes along well with what I have trying to download for my e-database of misc survival “stuff”(actual word used changed so as not to offend fecal mater). I have been trying to find and download as many small engine manuals and repair books I can find, especially for common ones. The same engines get used on many different things like lawn mowers, pressure washers, generators, etc.. same model different set up. The common manufacturers for small engines are Briggs and Stratton, Tecumseh, Honda, and Kohler. The Briggs and Stratton manuals were a little tough to find for free, mostly for the newer models. B&S if you go to their site want you to pay for each e-copy. I did do some searches and found sites where people that had the e-copies posted them for public viewing and download. Tecumseh I found lots for free. Haven’t gotten to Honda or Kohler yet. I figure by having the manuals it would help me to swap or repair an engine if or when they break down. By having e-copies it takes up very little space compared to having shelves loaded with paper copies that I might never use. The shelf space will get filled with paper copies of stuff that has a far greater chance of me using, more than once. Though I do have some general small engine repair books in paper copies added to the shelves already.

  2. On 4 cycle engines a major enemy is rust inside the cylinder. Always leave single cylinder engines on the compression stroke. This can be found as you pull on the engine’s starter cord; when the resistance is the most, you’re on the compression stroke. Leaving the engine this way closes the valves so atmospheric moisture cannot attack the cylinder walls.

    For multicylinder engines, the trick is to completely fill the cylinders with oil. An automotive salvage yard I worked for did this for the engines pulled from wrecks. The engine will smoke badly for awhile when it is resurrected, but it won’t be seized.

    Use fuel stabilizers in all small engine refueling containers, whether the fuel will be used within a short time or not. That way you’re relatively sure that you won’t leave bad gasoline in a carburetor you forgot to mothball. The additional cost is minimal considering the repairs avoided.

    For engines that must be ready to go at a moment’s notice, like a generator engine, the best defense is a regular schedule of test runs. Once per month is usually sufficient to keep the cylinder lubricated and rust free. Using fuel stabilizer and only putting small amounts in the tank at a time will keep the fuel fresh. It’s a good idea to have a spare spark plug and a can of starting fluid on hand for small engines that you depend on.

  3. gonewiththewind

    “Marvel Mystery Oil” Boy that brings me back to 55 years ago when I first started working on cars. We used to use that to lube almost everything. No one could tell me how the name was picked until finally some old mechanic said it first appeared in pipes from NG fields and since they were piping natural gas it was a mystery where it came from. Just kind of distilled out of raw NG and settled in the low places in the pipeline.

  4. I used the oil in an old Chevy I left in storage while deployed overseas for 3 years. Came back, charged the battery and it fired right up!

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