Why Your Lawn Mower Runs Better With Choke On and How To Correct It

One of the most common conditions that happen to lawnmowers is running only (or at least better) when the choke is on. While it might not seem like an issue at first, it will drain more fuel and can lead to other complications if you run it like this all the time. However, many people disregard this and run the mower anyway. So, is it bad to run a mower with the choke on?

If your mower runs better when the choke is on, it means the fuel/air mixture isn’t properly adjusted. This can be caused by too much air or too little fuel getting into the chamber. It’s bad to run a mower with the choke on because it can damage the engine.

Most mowers can’t even run with the choke one, but you should check what the problem is if yours does. No machinery should operate outside the normal functioning system. Before you start dealing with it yourself, you should first know what a choke is and how it works. Then you can detect the issues and deal with them accordingly.

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What is a choke on a mower?

Internal combustion engines often have a choke valve. It’s a valve that allows you to manually limit the amount of air getting into the carburetor, making the mixture heading into the chamber richer with fuel. It’s usually used during the ignition to allow an easier start. These kinds of engines are common in all kinds of vehicles, including automobiles.

On a lawnmower, the choke is the same thing as it is in a car. It’s a valve used to block the air intake. Usually, there’s a choke lever on the mower that you need to press during the ignition to get it started. Sometimes, it can feel like your mower runs better if you keep the choke on all the time, not just during the ignition.

Whether your mower can run with the choke on or not depends on what kind of a choke lever you have. You can have a choke lever separate from the throttle lever or have only the throttle lever with a choke mode integrated into it. In both cases, if your mower runs only with the choke on, or at least runs better in that position, there’s a problem you should adhere to.

Why does my mower run better with the choke on?

There are several reasons why your mower might be running better with the choke on. Keep in mind that none of the possible problems are too hard to handle yourself, but if you feel insecure about your repair skills, take your mower to a professional and repair it.

If your mower is running better when the choke is on, it means the mixture in the chamber is lean. Too much air is getting into the chamber, so when you “choke” the air intake, the mixture stabilizes, making the mower run better. Air leaks are quite common and can happen anywhere around the chamber. Most commonly, it’s the carburetor.

Sometimes, it can be the other way around. Due to a clog, or a malfunction on the carburetor, it is possible that not enough fuel is getting into the mixture. Therefore, lowering the amount of air inside the chamber levels it to a degree, making the mower run better. You would feel a significant drop in performance, though, and the engine might overheat soon.

Finally, there might be contamination in the fuel system. That means a foreign body caused a clog somewhere in the system: the carburetor, the fuel intake area, the fuel tank, etc. If none of these are the case, then you might need to switch to a fuel with a lower alcohol percentage. It costs a bit more but works a lot better regardless of the type of your mower.

Is it bad to run a mower with the choke on?

You should never run your mower with the choke on for longer than five minutes, which is the approximate warm-up time on most mowers. If you do, it can lead to increased fuel consumption, faster wearing of the elements of the fuel system, engine overheating, and finally, significant engine damage. 

Even if nothing significant happens to the engine, operating outside of the normal conditions for a longer period can lead to issues with other parts of your mower that aren’t necessarily a part of the fuel and ignition system.

While none of these things might happen right away, it’s much more cost-effective to deal with the issue right away. Regardless of what type of malfunction it might be, it will not be an expensive fix-up. In most cases, you can fix it yourself without paying anything extra.

How To Fix It

No matter how experienced you are, if you are not a professional mechanic, I always advise everybody to see a professional and ensure everything runs as it should. But, if you decide you want to do it yourself, fixing the choke problem on your mower isn’t hard in any case.

If there’s an air leak somewhere and too much air is getting into the chamber, try finding where the leak is. Tighten all the valves and pipes, leading air into the carburetor. Inspect the fuel lines for cracks, and if you have a manual fuel primer, check it for cracks or leaks as well.

If there’s contamination somewhere in the fuel system, you need to clean it thoroughly. Use a carb cleaner to clean the carburetor properly from debris and varnish. Drain the fuel tank and clean it thoroughly as well. Make sure all the fuel lines and pipes are clean and put everything back together.

If there are no cracks or leaks, and the entire system is clean, the only other reason can be a broken part of the mower unrelated to the fuel system, or the fuel you are using doesn’t match the engine. Using non-alcoholic fuels usually does the trick.

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