Unfortunately, we hear this question asked more often than ever before. Although it may have something to do with your E3 Car Spark Plug, it is more likely the result of using E10 gasoline, especially if you live in a hot, humid area of the country. Since the spark plug is the easiest place to start, take your spark plug wrench and carefully remove the plug for inspection. NOTE: If the top of the motor is dirty or there is a buildup of debris around the base of the plug, you should use a brush to clean before removing the plug. As always, you want to prevent anything from falling into the spark hole.
To keep your small engine running smoothly, make sure you know the special considerations for using E-10 gas.
Now, inspect the bottom of the spark plug for signs of excessive wear or a heavy build up carbon deposits. If need be, replace the used plug with the correct E3 Spark Plug for your particular engine. You can go to the E3 Spark Plugs Catalog page and select the Cross Reference Guide for your lawn & garden spark plug, powersports spark plug or motorcycle spark plug. Don’t forget to check the spark plug gap and always install your new plug using the correct torque specifications to avoid blow-by or damage to the internal threads. Assuming this did not resolve your problem, we will move to the next step.
Today, the majority of the fuel that you buy at any gas station or convenience store is going to contain around 10% of Ethanol (often referred to as E10 gas). The government’s Renewable Fuel Standard Program has required that Ethanol be blended with gasoline as a “Greener Alternative” to more harmful oxygenators such as lead or MTBE (methyl-tertiary-butyl-ether). The biggest problem with using the grain or sugarcane based fuel additive is that it is an alcohol. As the alcohol naturally separates from the petroleum-based gasoline, it has an affinity for attracting water.
This instability is called “phase separation” and has reduced the shelf life of the gasoline that remains in your small engine’s tank or that which is stored in your gasoline can. Most experts agree that under ideal conditions the shelf life of E10 gas is only about 3 months. If you live in hotter, more humid climates, it is much less. Once the fuel is contaminated, the bad gas can cause filters and carburetors to become clogged as unprotected rubber hoses and plastic parts actually begin to dissolve. Although some fuel stabilizers can help, there really isn’t a miracle product available for today’s cheaper small engines.
In time, we will likely find an alternative to Ethanol as a gasoline oxygenator, or even better, an alternative to petroleum-based fuels. But, until that happens, you should try to limit the length of time that E10 is kept in either your small engine’s gas tank or fill can. If your motor requires the choke to be engaged (even slightly), it is likely time to thoroughly clean the fuel lines, filters and carburetor. After that, try to limit the amount of time that you leave E10 in tanks or cans. Whenever possible, run the tank dry before storing your lawn equipment, mower, scooter, go kart or other powersports equipment. Many of these small engines also have a drain plug at the bottom of the carburetor bowl for that very purpose.
FAQs
If a motorcycle or ATV only runs with the choke on, it's because the richer “choke on” mixture is actually closer to the engine's normal operating fuel mixture than the leaner “choke off” mixture. So when the choke is turned off, the engine gets too little fuel and too much air for it to run and it stalls.
Why does my small engine only run when choked? ›
An engine that requires the choking (partial or full) after initial engine warm up is an indication that the engine fuel air mixture system is out of adjustment. Leaving the choke on while operating will result in excessive fuel consumption, irregular engine power performance and eventually may even damage the engine.
Why does my carb run better with the choke on? ›
When the engine is cold, it needs slightly more fuel in the fuel/air mixture to start, which is what the choke does. The choke increases the amount of fuel in the mixture, creating a richer mixture, allowing the engine to function at its best until it warms up enough to run on its normal operating fuel mixture.
Why does my bike only run good on choke? ›
If your dirt bike or ATV only runs on a choke, it could be that the fuel isn't getting to the engine. This could be caused by a number of things, including: A clogged fuel filter. A clogged fuel line.
Is it bad to run with the choke on? ›
Short-term use of the choke won't damage the engine, but if the fuel-air ratio is too high, it might clog the spark plugs. You should not ride for extended periods with the choke on. The solvents in the rich mixture may cause the cylinder walls to become worn down and cause the engine oil to burn.
What does the choke do on a small engine? ›
When an engine starts, it needs a rich fuel-to-air mixture. Chokes are designed to close off or "choke" the air supply in order to provide the proper ratio of fuel to air. An engine needs more air as it warms up, so the choke needs to open to allow more air.
What happens if you leave the choke on too long? ›
Last but not least, remember that leaving your choke on for extended periods will inevitably lead to higher fuel consumption. Only use it when absolutely necessary and release it as your engine warms up. Inspect the linkage and thermostat for damage or wear; check for vacuum leaks.
Can you clean a small engine carburetor without removing it? ›
Use carburetor cleaner to remove deposits, clogs & debris
Deposits inside the carburetor can clog fuel and air passages and reduce performance or stop the engine altogether. Luckily, you can take care of many of these problems quickly and easily; often without even removing the carburetor from the engine.
Can you run a motor with the choke on? ›
Limited Air Supply. If you leave the choke closed while the engine is running, you're essentially limiting the air supply to your engine. It's like trying to breathe with a scarf tightly wound around your nose and mouth. As you can imagine, that wouldn't be very comfortable, and neither is it for your engine.
Why does my Kohler engine only run on full choke? ›
The reason your engine would only run on full choke, is because your carburetor likely has a partially clogged jet or fuel passage. Check to make sure your fuel is flowing freely from your fuel tank to your carburetor.
By restricting the flow of air into the throat of the carburetor, the choke valve reduces the pressure inside the throat, which causes a proportionally greater amount of fuel to be pushed from the main jet into the combustion chamber during cold-running operation.
Is it OK to run bike with choke on? ›
Can I ride a bike with its choke on? It's not recommended. Doing so can flood the engine with excess fuel, increasing fuel consumption and potentially damaging the spark plugs.
Why does my riding lawn mower only run on choke? ›
The engine runs until the choke is opened. The fuel supply is then starved by the blocked fuel passages, and the engine dies. You have a couple of choices to solve this problem: clean the carburetor or replace it. Most carburetors can be cleaned and made to run like new again.
Why won't my bike idle without a choke? ›
When does the bike run only with a choke? This mainly happens when there is dirt in and around the parts of the carburetor. The areas of concern here include fuel lines, petco*ck, pilot jets, or fuel filters. The dirt blocks the fuel passage and it cannot reach the carburetor properly.
Is it okay to run engine on choke? ›
If you forget to turn off the choke after starting the engine, it will continue to run rich, meaning there will be more fuel and less air. This can result in the engine operating inefficiently, consuming more fuel than necessary, producing excessive exhaust emissions, and even causing the spark plugs to foul.
What are the benefits of a choke? ›
Their purpose is to shape the spread of the shot "cloud" or "string" to gain better range and accuracy, and to deliver the optimum pattern of pellet density, for the particular target, depending on its size, range, aspect and whether it is traveling towards, across or away from the shooter.
What happens if choke is always on? ›
The choke should be closed immediately after the engine starts running. If you leave it open, it can flood your engine with excess fuel, resulting in increased fuel consumption and reduced efficiency. Moreover, it can also damage the spark plugs.
To keep your small engine running smoothly, make sure you know the special considerations for using E-10 gas.