Many, many readers of DoItYourself have reached out for advice regarding a common problem—a Honda lawn mower that fires up, but dies again after a few seconds. Specifically, Honda owners reported the mower would fire up easily, perhaps running for up to 30 seconds, and then die abruptly. At this point, the mower often won’t fire up again unless it is allowed to sit for a period of time.
Although this can be an exceptionally frustrating problem, the fix is likely as simple as replacing the spark plug, although if you’re familiar with the workings of engines it might sound like a carburetor issue. In reality, while the spark plug and carburetor are both likely candidates, there are other culprits to consider when your Honda lawn mower just isn’t running the way it should.
Step 1 - Check the Fuel Level
Look, it wouldn’t be the first time a user forgot to see if the lawn mower had gas and went through a bunch of extra work unnecessarily, so trust us on this one—check the gas. Even if your tank is not completely empty, try adding a bit more gas, priming if your machine has the feature, and use the choke when starting.
Step 2 - Check for Bad Gas
If your lawn mower has sat over the winter with gas in the tank or the mower is used but new to you, drain the gas and start with a fresh supply. The quality of gas matters and bad gas can actually cause big issues so don’t tempt fate on this one.
Step 3 - Check the Oil
Many Honda lawn mowers have a separate compartment for the oil. The machine draws fuel and oil in the right combination when running. If the ratio is out of balance, the mower may fail to run properly. To evaluate your oil level, use the measurement on the side of opaque holding tanks or use the dipstick to ensure there is enough oil in the reservoir. Always check with the owner’s manual to verify you’re using the proper type of oil.
Step 4 - Evaluate the Spark Plug and Wire
While sharing stories in the DIY forum the vast majority of readers found the solution was the simple replacement of a $4 spark plug. To evaluate whether this is your issue, start by making sure the spark plug wire is making a good connection. Press down on it and wiggle it back and forth a bit for confirmation. Try the mower.
Next, remove the spark plug wire to eliminate the risk of shock and unscrew the spark plug. If you see a black build up or any sediment on the spark plug, it could be bad. However, it’s very important to note the many malfunctioning spark plugs look as good as new, so the visual test is not always the best test. You can try scrubbing the spark plug to improve contact and see if that solves the problem.
This is always worth a shot. If it's not looking great, though, the easiest, fastest, and least expensive route for this repair is likely just to replace the plug.
Note: Be sure to properly gap your new spark plug according to manufacturer recommendations.
Step 5 - Adjust the Choke
The choke can be a sticking point in the amount of gas your mower receives. Check your owner’s manual for the location and care for your particular model. Sometimes a simple adjustment will solve the problem.
Step 6 - Look for Recalls
When you get a new lawn mower be sure to register the machine. This allows the company to contact you in the case of a recall. For example, some time back, some Honda models had a yellow plastic piece causing the engine to cut out. The recall allowed the company to replace the part with a metal one, solving the problem.
Step 7 - Clean the Carburetor
We saved this as your last step because it is the most time consumptive. Try the simple solutions above before digging into your carburetor, especially if you’re not familiar with working on engines.
If you’ve verified you have fresh gas, your carburetor may not be functioning properly and is likely a result of gunk build up. Start by taking the cover off your lawn mower carburetor. Manually press the flap that allows fuel into the carburetor to see if it acts as expected. Look for sticky parts and black build up. Take a picture of each part as you disassemble the carb for reference when putting it back together. Clean each part using a good carb cleaner and a brush. The reassemble the carburetor and test to see if your issue is resolved.