Outboard Motor Will Only Run With Choke On? The 80 Top Answers

If your Predator 212 or other engine only runs with the choke on, the problem is with the air/fuel mixture. More specifically, the engine is getting too much air but not enough fuel for combustion. So when you turn on the choke, some of the air is blocked and the engine runs smoothly.

The solution is pretty simple, you can either buy a new carburetor or clean the pilot and main jets on your existing carburetor. Usually the culprit is a clogged pilot jet, but you should clean your entire carburetor to be sure.

Here is a step-by-step guide:

1. Remove the air filter

Removing the airbox is fairly easy, just take a 10mm socket and unscrew the 2 screws shown in the picture. Make sure the lever is in the middle for easy removal. Once the bolts are out you will need to disconnect the air box from the breather hose that connects to the cylinder head. Then just pull out the box and you can see the carburetor.

2. Remove the carburetor from the engine

Once you take off the airbox you can see the carburetor (as shown in the picture). To remove the carburetor: Using pliers, stretch the fuel line clamp. Disconnect the fuel line and block the hose with either pliers or a screw or fuel will leak out. Move the carburetor forward slightly to slightly loosen the spring and rod. Unhook the spring and rod.

3. Dismantling the carburetor

As mentioned, the most likely component causing this problem is the pilot jet, so let’s take the pilot jet out first.

The pilot/idle jet is located just below the idle screw. To take it off, you must first loosen the idle screw. The nozzle itself is pressed into the hole with an o-ring, you will need a flat head screwdriver to take it out. To remove the main jet, you must first drain the fuel in the carburetor by unscrewing the drain plug, and then loosening the main screw. Then remove the bowl.

4. Clean pilot jet and main jet

This is what an idle/pilot jet will look like. The brass underneath has a small hole so it sucks the fuel out of the carburetor chamber. In your case, the hole is most likely clogged, which is causing the problem. Either take a carburetor cleaner and spray it through the hole, or take a fine wire and thread it through the hole.

This will solve the problem at low speed, but if your engine stalls in the later stages/higher RPM, the main jet is likely the problem.

This is the main jet that you will see when you remove the bowl. (There will also be a plastic float that was removed before this picture was taken) Take a flathead screwdriver and take out the main jet. Similar to pilot jet cleaning, spray some carburetor cleaner or run a thin wire through the holes. If you tap the main jet reservoir lightly, the emulsion tube will also fall out. You can/should clean that too.

5. Assemble

Finally put everything back together. Be sure to install the gaskets that came with the carburetor. If they broke when you removed them, you’ll need to get new gaskets.

alternative

Instead of cleaning, you can replace the carburetor. A Chinese replacement carburetor is only $10 and comes with gaskets etc.

How to adjust the carburetor on a small two-stroke engine

The carburetor of a two-stroke engine has a mixture setting for idle speed and a mixture setting for high speed. Adjusting the carburetor for this type of engine is part of the process known as tuning the engine. Tuning a two-stroke engine keeps it running at peak performance. You can adjust the mixture settings on the carburetor by turning two screws located on the carburetor.

instructions

Main reasons why boats fail, stutter or lose performance

In reality, this problem can be caused by a variety of issues. Anything from dirty or corroded spark plug wires to deposits in the gas can cause sputtering or loss of power. The first step is to determine the cause of the problem. The easiest way to do this is to eliminate the simplest explanation first and work your way outward until you find the problem. The most obvious answer is fuel. Just as people lose track of time, it’s just as easy to lose track of your fuel consumption. If you have a lot of fuel then the next place to look is the fuel filter. Hope you have a spare filter with you. If not, remove the current filter and see if you can remove debris. With the filter off, make sure there is no water in the fuel. Remember, I/O boat owners must bleed the engine box before restarting the engine. If you forget this important step, the clogged filter will seem like nothing compared to your new problem. So if you have gas and your filter is fine, the next thing to look for is the spark plugs. Check them one by one and inspect the wires while you’re there. Seriously, only take off one wire at a time and make sure to put it back in before removing another wire. The last thing you need is to take off all the wires, only to find you don’t know the order of placement, to put them back. If one or more spark plugs are fouled, do your best to clean them and remove as much dirt as possible. A rag or loose piece of cloth should remove some of the debris. You can use a knife or similar object to scrape off large deposits, but be careful not to damage your spark plug or accidentally adjust your spark plug gap. Inspecting the connector wires is as simple as checking for signs of aging such as cracks or brittleness. If you still haven’t found the problem, check your terminals and connection points. Signs of corrosion, damage, or breakage indicate it’s time to replace some connectors. Make sure you use the correct crimping tool when installing the terminals or you risk a new problem by creating a weak point in your electrical system. The right tool guarantees the right crimp every time and reduces the risk of problems later. If you’ve checked all of the above and everything looks fine, it’s time to call a mechanic.

prevention

The problem is that sometimes you just get bad fuel. When fuel is delivered to gas stations, the last ones to receive the fuel get the garbage that has accumulated on the bottom of the tank. To be honest this isn’t really a big issue and it’s more likely that your gas has gone bad from sitting or there is water build up in your tank. If you leave a fuel tank empty, condensation will form and we all know that gas and water don’t mix. If you won’t be using your boat for a while, fill the tank as full as possible to avoid condensation. If you plan to keep it upright for more than 3 or 4 months, add a fuel stabilizer. The other way to avoid this problem is to regularly clean and replace your spark plugs and fuel filter. Spark plugs are a fairly simple change and should be done based on engine usage or a period of time, whichever comes first. Consult your manufacturer and spark plug information to determine when is the right time to replace. Replace your spark plug leads at the first sign of wear. Even if only one looks bad, change them all. They should all be about the same age. So if one fails, it’s best to play it safe and replace them all. It’s a good idea to have a basic toolbox on board with basic terminals and installation tools. That way you won’t be caught off-guard should a problem arise. A simple tool chest and tool kit makes a world of difference.

Needed tools:

Nut and ratchet set

Clean rags

Replacement fuel filter

filter key

Fuel stabilizer (when the boat is upright)

Proper crimping tool and terminals

Choosing the right crimpers:

When choosing the right crimping tool for your boat, consider one that is suitable for epoxy heat shrink terminals. They are the best choice for a marine environment as they offer added protection against moisture, corrosion and abrasion. Using other types of connectors in marine conditions is acceptable, but will make your electrical system more vulnerable than it needs to be. To properly install a heat shrink tube, make sure you use a tool that fits the most common sizes. The VTTR-50 can crimp 22AWG to 8AWG without changing die sets. It offers repeatability and reliability, which is why it is often chosen for use on production lines. Make sure you don’t get stuck on the water without the right tool.

A multimeter might help:

If you find a problem quickly, you can solve it much faster. Using a multimeter is an easy way to determine if you have an underlying electrical issue. A digital multimeter is used to monitor and test a boat’s electrical system. Pacer Group carries a multifunction meter that is ideal for safety checking and troubleshooting a boat’s electrical system. You can either use the clamp meter to collect information directly from wires, or you can use the included test leads directly on exposed contact points. The advantage of using the clamp is that you can measure the current in your boat’s wiring without disturbing circuits or making contact with live terminals

It’s a sunny summer day and you’ve got your fishing rod in hand and ready for an afternoon of fun and excitement on the water. Your friends get on the boat and you prepare to leave when the worst-case scenario occurs – nothing. You turn the key in your boat’s ignition, but all you hear is the lapping of the waves on the shore. Your boat won’t start.

Nothing can ruin a boat trip faster than an engine failure. Fortunately, there may be a simple answer to why your boat engine won’t start, and a simple solution to the problem. While it may be tempting to leave the ignition on and hope for the best, that only drains the battery and makes the problem worse. You’ll be back on the water faster if you try one of these solutions to common boat engine problems.

Common causes and solutions for a boat engine that will not start

Although boat engines have become more complex as technology has advanced, most marine engines still operate on the same simple principles. Boat engines need ignition, fuel, air, compression and exhaust to start and run smoothly. If any of these items are missing due to broken or damaged parts, your engine may not start and may have trouble starting. Consider this list of common reasons why your boat engine isn’t detecting and fixing the problem quickly.

1. Security features enabled

In the excitement of cruising the water, it’s easy to forget to disable the safety features that prevent your boat from starting. Most modern boats are equipped with a safety lanyard or ignition circuit breaker that must remain connected while the boat is in motion. If the safety line has become detached for any reason, your boat’s engine may start but not fire, or it may not turn at all. If your boat has an ignition disconnect switch, make sure it is in the on position.

2. Boot sequence error

Even the most experienced boaters make mistakes from time to time. Before you disassemble your marine engine, double check that you are following the correct starting sequence for your boat. Depending on your engine type, you may need to throttle the engine by putting the key in the ignition or pulling out the manual choke knob on the engine. In colder weather, your boat may need a little more choke than usual to start.

If you just bought your boat or it’s been a while since you’ve been on the water, take a few minutes to read your boat’s manual to make sure you’re following the proper pre-ignition protocol.

3. Boot not idle

Most boats need to be idle before starting the engine. When your boat is in gear, the engine will not start, but other components such as the lights and gauges will work. Make sure the gear shifter is firmly in neutral and the lever is in the mid-position between forward and reverse gears.

4. Dead or disconnected battery

If your starter engages but the engine cranks very slowly, your boat battery may be low. If the engine does not start at all, the battery may be dead. Check the voltage of your batteries with a voltmeter and charge the batteries to around 12.6 volts for a full charge. If the battery isn’t charging or holding a charge, you may need to have it replaced.

For boats equipped with two batteries or a battery switch, make sure it is set to On or Both before attempting to start your boat. While a battery switch is an excellent feature to prevent battery drain, it can also be the reason your boat won’t start if you forget to turn it back on.

If you have checked the battery switch and charged the batteries but your boat engine still will not start, check the battery cables. Make sure the connections between the engine and battery are not loose or corroded. Reconnect or replace any disconnected or damaged battery cables.

5. Engine not primed

Another common starting mistake is trying to start the boat before the engine has properly primed. Depending on your boat model and year, you may need to turn the key to the “on” position and wait for the engine to boot. If your boat does not start after priming, make sure fuel is getting to the engine and the primer is not damaged.

If your boat has an electric primer, check that fuel is flowing properly by removing one of the fuel hoses connecting the primer to the carburetor or engine intake. Have a friend or family member put the key in the ignition to start the engine while you watch for fuel. Be sure to use a bucket or cup to catch the fuel and prevent it from spilling.

If your boat has a pressurized fuel system, verify that it is working properly by pumping the primer ball. After a few squeezes, the primer bulb should solidify, indicating the fuel system is pressurized. If this is not the case, check the fuel lines, engine, tank and filter for leaks. A primer ball with a defective valve inside can also prevent your fuel system from being sufficiently pressurized. If the fuel tank primer is not working properly, you may need to replace it before hitting the water.

6. Empty the gas tank

Another reason fuel may not flow to your marine engine is because there is nothing in your gas tank at all. Even if you’re sure you remembered to fill up after your last boating adventure, it doesn’t hurt to double-check – or take some extra fuel with you, just in case.

7. Loose or pinched fuel lines

If the fuel lines in your marine engine are kinked or pinched, it will block fuel flow to the engine. Make sure fuel lines are not clogged and replace damaged fuel lines. The fuel line couplings and fittings in your boat’s engine can also become loose over time. Make sure all connections are tight and all o-rings in the fuel system are intact. A ruptured o-ring or loose connection can allow air to enter the fuel lines and prevent the boat from starting.

8. Blocked ventilation openings or exhaust

Your boat’s fuel tank must be adequately ventilated in order for it to ignite. Make sure all gas tank vents are open and not blocked. A clogged engine exhaust is another common reason why a boat won’t start – especially if you recently took the boat out of storage. During winter storage, rodents sometimes build nests in the exhaust outlets of boat engines, blocking proper airflow and preventing the engine from starting.

9. Water or dirt in the fuel system

Marine fuel systems can sometimes collect water and dust that prevent the engine from operating properly. If there is water in your fuel system, you will see a settled and defined layer of water under the fuel. Drain the water and change your fuel filter. If you see dirt buildup in the fuel tank or filters, flush the fuel system and then refill with new fuel.

10. Carburettor settings too lean

The carburetors in your boat engine control the flow of air and fuel to your engine. If your carburetors are clogged or you have adjusted them incorrectly, not enough fuel will get into the engine to start or run it. If the carburetor has visible dirt or grime, clean it thoroughly. After the carburetor is clean, adjust the carburetor settings to provide the correct air/fuel mixture for your boat’s engine, and then attempt to start the boat again.

11. Faulty spark plugs

Dirty or damaged spark plugs make it difficult to start your engine. Inspect your spark plugs and replace defective or fouled spark plugs. Improperly gapped spark plugs in your marine engine can also prevent your boat from starting by delaying engine combustion. If you’ve noticed that your boat’s engine is hesitating, idling erratically, or generally performing poorly, it may be a sign that your spark plugs need adjusting. Correct the gap setting on your spark plugs or have a certified marine mechanic adjust them for you.

12. Improperly split ignition points

Similar to your boat’s spark plugs, the ignition points in your boat’s engine must be correct, clean and tight in order for your engine to start. Adjust your ignition points to the correct spacing and remove any dirt build-up. If the ignition points are damaged or broken, consult a professional mechanic for a repair.

13. Bent manual choke linkage

If your boat’s engine manual choke linkage is bent or dented, the engine may not start. If the bend is small, you can often readjust it with a hammer or pliers. A major dent or structural damage to the choke linkage may require a complete replacement. If your boat’s engine has an automatic choke, it may be misaligned and need to be corrected.

14. Improper engine timing and synchronization

If the timing and synchronization in your boat engine is not set correctly, you should consult a professional mechanic as your engine may have internal damage or a defective flywheel. If the flywheel becomes disconnected due to a sheared fastener or other damage, the crankshaft will not rotate when you try to start the boat, interfering with engine timing. A mechanic can replace the defective part to correct the engine timing.

15. Damaged electrical insulation or wires

Continued wear and tear can cause the insulation in your boat’s electrical system to fray, or the wires to become loose or break. Check all wiring and insulation and replace damaged wiring. If you’re itching to get in the water, you can use electrical tape as a temporary solution to frayed insulation. However, be sure to make a proper repair when you get back to shore.

16. Sticking or damaged diaphragm valves

Two-stroke marine engines contain reed valves that help control airflow to the engine. Reed valves sit below the carburetor to prevent the air/fuel mixture from escaping the engine cylinder again after it has been forced out of the carburetor. If the reed valves are chipped, cracked, or improperly seated, air and fuel can escape from the cylinders instead of being compressed by the pistons. This problem causes the engine to run lean and eventually makes starting difficult.

Fortunately, replacing diaphragm valves is relatively easy once you identify the damaged valve. If you think your boat engine has reed valves that are not sealing properly, inspect them for any visible cracks or tears. If the valves are sealing properly, you shouldn’t be able to see any light.

17. Weak capacitor or coil

The ignition coil and capacitor in your boat engine wear out with regular use. If you take your boat out frequently, these parts can be the reason why your boat won’t start. Replace the ignition coil and capacitor when they appear worn or weak.

18. Damaged distributor cap or rotor

The distributor and rotor in your boat engine are responsible for delivering voltage from the ignition coil into the cylinders to ignite the fuel-air mixture. If the distributor cap or rotor is damaged or cracked, your boat’s ignition will not work properly. Replace the damaged distributor cap or rotor, and then try starting the engine again.

This list of common reasons why a boat engine will not start is a good starting point for troubleshooting a defective boat engine. If your boat still won’t start after trying these solutions, contact a certified boat mechanic to inspect your engine and pinpoint the problem.

Rely on a high-performance engine in your formula boat

If you want to avoid getting stuck at the dock, choose a reliable and quality motor for your boat. Although an excellent marine engine won’t prevent you from forgetting to fill up your gas tank or accidentally draining your battery by playing your stereo, a quality engine will offer reliable long-term operation with fewer hiccups than an inferior model. Premium marine engines are designed to provide years of lasting durability, exciting performance and trouble-free operation.

At Formula Boats, we’re dedicated to building the best powerboats on the water. This means that we build our luxury boats with the highest quality materials and the very best equipment, including your choice of a high performance engine from one of the finest marine engine manufacturers. Formula offers sterndrives and outboards from three leading manufacturers – Ilmor, Volvo Penta and Mercury® Mercruiser®. Each brand offers different benefits to meet your unique boating preferences.

Mercury: Mercury is one of the few marine engine manufacturers that builds their engines from scratch rather than marinating car engines. Their boat engines offer superior corrosion resistance, excellent handling and a whole lot of speed.

Mercury is one of the few marine engine manufacturers that builds their engines from scratch rather than marinating car engines. Their boat engines offer superior corrosion resistance, excellent handling and a whole lot of speed. Volvo: Focused on fuel efficiency and performance, Volvo Penta produces lightweight and durable engines from marinated aluminum.

With a focus on fuel efficiency and performance, Volvo Penta produces lightweight and durable aluminum marinated engines. Ilmor: Ilmor is another trusted name in marine engines, offering smooth shifting, exceptional maneuverability and all the power you need to get the most out of your Formula boat.

Because Formula powerboats are fully customizable, you can choose the perfect engine that suits your preferences in power and performance. Our marine engines range from 250 to 430 hp, with top speeds in excess of 60 mph on some models. Whether you’re racing through the waves or prefer a leisurely cruise across the bay, with Formula you can choose how much horsepower you want and choose a marine engine propulsion system that suits your boating style.

To offer a truly personalized boating experience, Formula Boats even offers sterndrive and outboard engines for many of our powerboat models. Whether you prefer the sleek looks of a sterndrive or value the fuel efficiency of an outboard, Formula has the right powerboat engine for you.

Contact Formula Boats to find out more

In addition to our powerful, high-performance engines, Formula Boats offers many other top-notch features including custom seating areas, expanded swim platforms, advanced GPS systems, shade structures, air conditioning, entertainment options, lighting features and much more. With advanced engineering and unmatched performance, Formula’s world-class powerboats offer a leisure boating experience like no other. If you’re ready to hit the water in luxury and style, start designing your Formula boat today or contact us to learn more about building your dream powerboat with Formula.

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carburetor

If your mower starts and runs with the choke on but stalls when the choke is off, there may be a problem with the carburetor. The carburetor brings air and fuel together and mixes them in the perfect ratio for combustion before they enter the engine. There are several passages in the carburetor that allow fuel to enter the airflow, depending on how the throttle is set. The idle shift when the throttle is almost closed and the engine is idling. The transition shift when the throttle goes from idle to full throttle. At full throttle, the main jet is used. The choke helps provide extra fuel when the engine is first started. When closed, the choke plate blocks most of the incoming air from entering the carburetor venturi. This creates additional negative pressure in the venturi and also forces air to…

If your mower starts and runs with the choke on but stalls when the choke is off, there may be a problem with the carburetor. The carburetor brings air and fuel together and mixes them in the perfect ratio for combustion before they enter the engine. There are several passages in the carburetor that allow fuel to enter the airflow, depending on how the throttle is set. The idle shift when the throttle is almost closed and the engine is idling. The transition shift when the throttle goes from idle to full throttle. At full throttle, the main jet is used. The choke helps provide extra fuel when the engine is first started. When closed, the choke plate blocks most of the incoming air from entering the carburetor venturi. This creates additional vacuum in the venturi and also forces air to be drawn in through an opening in the front of the carburetor body. This port leads to the air space at the top of the bowl. This air pressurizes the space above the fuel in the bowl, forcing the fuel to flow out of the main jet and into the venturi. This rich fuel mixture makes it easier to start a cold engine. Once the engine starts and runs for a few seconds, the choke opens and the other fuel passages in the carburetor do their job as usual. An engine that fires and runs with the choke closed but stalls when the choke is opened likely has deposits at least partially blocking the fuel passages in the carburetor. In this condition, the closed choke provides enough additional fuel to enter the engine to overcome the lack of fuel flowing through the other passages. The engine runs until the choke is opened. The fuel supply is then starved by the clogged fuel passages and the engine stalls. You have a few options to solve this problem: clean the carburetor or replace it. Most carburetors can be cleaned and made working again. Cleaning a carburetor is not difficult, but it does require the carburetor to be disassembled for the most part. Replacing a carburetor is a quick and easy repair. In some cases, the new carburetor is so cheap that there really is no point in cleaning the old one. Usually, the cost of a new carburetor versus your repair experience and skill will determine whether to clean or replace it. To begin cleaning your carburetor, remove it from the mower and carefully disassemble its components. Remove the bowl and drain any fuel from it. Note that there is one gasket that seals the bowl to the carburetor and one to seal the bowl screw. If any of the seals are damaged or cracked, they should be replaced. Remove the pin on which the float pivots and the dispensing needle. The dispensing tip should be inspected for corrosion and wear at the tip of the tip. Dirt or corrosion on the tip or needle seat will prevent the needle from fully closing. This will keep fuel flowing into the bowl and exiting the throat of the carburetor. Remove the main jet and emulsion tube. Dirt or corrosion can clog the tiny orifice in the nozzle or the series of holes cross-drilled in the emulsion tube. These tiny openings can be cleaned with carburetor cleaner and compressed air. If necessary, fishing line can be used to remove dirt from the openings. Never use anything metallic when cleaning a carburetor. Metal picks, wire, or other tools can easily resize the openings and change the amount of fuel that can flow through them. Next comes the pilot jet. There is often a plug or screw on the carburetor body that covers the pilot jet. Access the pilot jet and clean it out with carburetor cleaner, compressed air, and fishing line if necessary. After the carburetor is disassembled, you can clean the carburetor body and shell. Use carburetor cleaner to thoroughly clean every tiny passage in the carburetor. Also clean the bowl, main jet, pilot jet and emulsion tube with the carburetor cleaner. Use compressed air to remove any carburetor cleaner residue from each component. If you have an ultrasonic cleaner in your tool arsenal, it will work great to clean your carburetor. Ultrasonic cleaners do an excellent job of cleaning the tiny openings and passageways in a carburetor. Often an ultrasound is the only way to salvage a badly clogged carburetor. Replace any parts in the carburetor that were too dirty to clean or damaged by corrosion. After cleaning, carefully reassemble the carburetor and reinstall it on the mower.

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Here at Venhill, our mission is to help people get more out of their bikes, quads, cars and karts through innovative products and a passionate workforce.

Something that can often come up for new bike owners is the challenge of starting a bike in cold conditions.

Why can it be difficult to start a motorcycle on a cold winter morning?

While most new bikes have electronic fuel injection (EFI) to start the engine in colder temperatures, older models (and some new ones) often don’t have such a luxury. Luckily, these carbureted engines can fight cold temperatures with a choke valve.

But what exactly is a choke valve or cable and what do bike owners need to know about it?

This article dives into the world of choke valves and cables and will help you understand how they benefit motorcycles.

What is a throttle valve?

A throttle valve/cable is used to restrict the flow of air in an engine’s carburetor. This helps enrich the fuel-air mixture, improving the ability to start an engine at low temperatures.

On carbureted bikes, a choke valve/cable helps ensure there is enough usable fuel to start the engine when the temperature and climatic conditions are low. The ratio of air and fuel required to start the engine changes with temperature due to the physics and thermodynamics behind combustion and air density.

A cold engine doesn’t vaporize fuel as well as it does in warmer conditions, so the choke helps enrich the mixture (either by adding more fuel or cutting off the airflow) to increase the amount of combustible vapor needed to start the engine engine is available.

Simply put, the choke is all about making more fuel available to the engine.

On a motorcycle, a throttle valve is likely to be a pull lever attached either directly to the carburetor or indirectly via a cable to the carburetor. If you need help finding the right type of cable for any part of your motorcycle, don’t hesitate to contact us here at Venhill. Our motorcycle cables are built to the highest standards, helping enthusiasts and professionals alike get more out of their bikes.

Each model and make of motorcycle uses choke valves and cables slightly differently. Some bikes use a choke to reduce airflow to enrich the mixture, while others use a fuel enrichment valve that increases the amount of fuel (as opposed to reducing airflow). Both types achieve the same thing, but can be adjusted differently depending on the model and bike brand.

Once the engine is running and warming up naturally, the throttle valve can be closed to reduce additional fuel consumption. Holding the valve open unnecessarily results in poor fuel efficiency.

Using a choke on a motorcycle

There is no harm in starting the engine with the choke. When it’s cold, getting things going can be a necessity.

Unnecessary use only leads to increased fuel consumption, but not damage to the vehicle.

Each bike can implement a choke system in its own way. This affects how motorcycle owners enrich the mixture in the carburetor.

Eventually riders will understand how long they have to use the choke to get things going. Depending on the temperature, this will likely vary as well.

There is also no set temperature that would be recommended to start using the choke. Instead, motorcycle owners should simply be aware of the benefits of using the choke. If the motorcycle is having trouble starting, this is the first thing to try.

Electronic fuel injection

An alternative to carburetors (and something that’s becoming increasingly popular on new bikes) is electronic fuel injection.

An EFI uses computers and sensors to better understand external conditions and help decide what the optimal airflow/fuel mixture should be. This reduces poor performance but mitigates excessive fuel consumption.

EFI systems can simply be an application that “injects” fuel into the airflow when it’s needed, e.g. in cold conditions.

An EFI system uses an engine control unit (ECU) to control the series of events to provide optimal engine performance. By reading and interpreting all the available data the sensors are gathering, the ECU can ensure the engine is getting the right amount of fuel and airflow to start. Through the use of technology and advanced sensors, this can make a motorcycle owner’s life a lot easier, with all of this being automated in the background. However, given the increasing use of applications, when there are problems, fixing them often requires a look at the electronics.

While some prefer the hands-on approach of carburetors and manual control of the choke, others may welcome a more automated approach. Whatever your preference, EFI systems are growing in use and popularity and will likely continue to grow in the motorcycle world.

Find out more with Venhill

Whether you’re a traditionalist and stick to carburetors or just bought a new bike with EFI, our range of motorcycle cables and products here at Venhill are designed to help you get more out of your bike. We ship our products to distributors across the world and sponsor some of the UK’s top MX and Superbike racing teams.

From throttle cables to handlebars and accessories, we strive to offer our customers only the best products.

Our parts finder is a great starting point, making it easy to find the relevant cables and hoses for your motorcycle for your individual circumstances and preferences.

Our team is always here to guide you in the right direction and make sure you are comfortable with whatever you need.

Contact us today.

See More: Types Of Motorcycle Engines

See More: Useful Motorcycle Fittings and Components Every Cable Designer Should Have

If you’re having trouble identifying the “on” and “off” positions of a choke switch, you’re not alone. Sometimes it may require a light to come on to tell if a switch is on or off, but in the case of a choke with no bulb what would the indicator be? Which symbol on a choke is on or off?

The choke icon is in the on position and restricts airflow to the engine when the lever is pointing to an angled or horizontal line. This can also be denoted by the words “choke”, “full choke” or “start”. When the choke is off or disengaged, the lever will point to a vertical line or the word “Run.”

There is a lot more to know about how a choke works and what those symbols or words mean. The concept isn’t difficult to grasp, so read the rest of this article and you’ll know everything you need to know about small motor chokes.

What position is “Choke On”?

For those not very familiar with mower or trimmer engines, knowing what a choke is used for and what the positions mean can be confusing. Understanding the simple operation of a choke will help you better understand what the position of the choke lever does.

First, why is it even called a choke? Your lawnmower’s (or other electrical device’s) choke function is used to control the air entering the cylinders and mixing with the fuel.

More specifically, when the choke is on, airflow is restricted and when it is off, air is free to enter. This means that the condition of the choke on your lawn equipment can determine how well it performs during use.

I’ll get into more of that later, but turning on the choke essentially keeps more fuel vapor in the engine and restricts most of the airflow that would dilute the fuel vapors. This concentrated fuel environment aids in starting and warming up the engine.

Now that we have an idea of ​​how the choke works it is ideal to know how to identify the ‘on’ and ‘off’ position of the choke on your lawn equipment.

How do you know if the choke is on or off?

Here, RustySkull Productions shows the “Choke” or “Choke On” location icon, also labeled “Start” here.

In most cases, the choke is a small lever or switch on one side of the mower. When the lever is pushed up or forward to a diagonal or horizontal line, the choke will engage. When the choke is on, the carburetor is blocked by a plate-like obstruction.

At this point the system can be said to be “choked” and if the lever is pulled down (or back) to a vertical line the choke will disengage. The obstruction is removed and air is allowed to flow into the vessel where it is combined with fuel.

If you only have one (usually red) switch to control the choke, all you need to practice are these two points:

First, the “I” indicates the choke is engaged or airflow is restricted.

Second, the “O” indicates that the choke has been turned off.

If your lawn mower suddenly shuts off or sounds like it’s struggling to stay on, you should check the choke lever before calling a technician. If the air/fuel ratio is imbalanced, the engine would struggle to run properly, so you’ll always want your choke lever in the right place when using the unit.

Another note: many times in the middle of a long job the engine would start stalling, leading me to adjust the choke and suspect something was wrong with the fuel/air ratio. Although I was usually right about the air ratio in the engine, I usually ended up running out of fuel.

Embarrassing then, but funny now.

Another interesting side point: Researchers are always looking for better ways to use fuels and engine design. Currently chokes are the primary way to control air and fuel entering a carburetor, but in the future this may not be needed.

In a technical article published on SAE.org, engineers and researchers alike are looking at ways to make engine starting easier and more energy efficient for users. Nowadays you can even see automatic throttles on many high-end models from most brands.

However, like most innovations, these come with their own problems.

Here are some other articles for you from LawncareGrandpa.com…

Is it bad to leave the choke on?

This question could go in three directions:

“Is it good to leave the choke in the on position when starting?

“Is it good to leave the choke on after turning the unit on?”

“Is it good to leave the choke on after using the lawnmower?”

The answer to any question about leaving a choke on is definitely no. When starting, the choke is only used to prime the engine. When operating a mower or other small power tool, operating with the choke engaged can indicate or cause problems. Throttles should be turned off for storage.

Leave the choke in the on position during starting

When the choke is on, fuel combustion is optimized for use.

In other words, the air-fuel ratio is controlled and the carburetor can function appropriately. This indicates that it is not only good but also important to turn on the choke before using the device in question.

This position helps when starting and warming up the engine.

Starting Tip: What I usually do to start a small choke engine is hit the intake piston 5 to 10 times with the choke fully open (—), depending on your equipment. I then pull the cord or turn the ignition switch (key) until the engine stalls. Then I reduce the choke to half ( / ) and start the engine. After a few seconds of warming up, I turn off the choke ( | ) to let the engine run normally with optimal air intake.

Now let’s look at the problems that trying to leave the choke on while running could cause or indicate it.

Leave the choke on during operation

Now that you’re in full swing, you might want to pull the choke lever down (or back) a bit. As long as the choke stays on, more fuel would be used, and if you don’t mind using a little more fuel to mow, you can leave it on throughout the process.

However, this may not be ideal for mowing operations that take up to an hour or more. Leaving the choke on for so long can not only cause the engine to use more fuel, it can also increase pollution and cause the system to heat up more than it needs to.

However, this is not the intended or optimal use of a choke. Most normally running engines will stall and smoke at full choke once started and warmed up. Mowers that are properly adjusted and operating with full choke use for extended periods will also have reduced power and movement.

There are two reasons your mower or other equipment may only run on full choke.”

There is some type of clogging in the fuel lines, fuel filter or air filter, reducing the amount of fuel that reaches the carburetor.

The fuel used has a sub-optimal octane mix due to the presence of water or other additives.

Finding and fixing these problems can improve fuel efficiency and operation. For purposes of our discussion here, it can also fix the problem that is causing your mower, blower or weedeater to only run on full choke.

Do you leave the choke in the on position when storing?

After the lawn is mowed to your satisfaction, what do you do? Turn off the power and leave the choke on so you don’t have to worry about it next time?

The simple answer to that is “choke off”.

The purpose of the choke is to warm up the system during operation and when the lawn mower is turned off it is advisable to turn off the choke as well.

Even leaving the choke in the “half” position is not a good idea when storing. In some cases, after starting in the full position, the choke lever can be pulled halfway down and the mowing equipment has warmed up to reduce fuel burn.

Understand the role of the choke in a lawn mower

The choke feature on your lawn mower is designed to virtually throttle the carburetor and restrict airflow. This is to allow the correct amount of air and fuel to mix during operation of the unit. As long as the choke is on, fuel will enter the vessel, and the longer it stays on, the more fuel will be used in the process.

If the fuel supply is too high, it will affect the operation of the lawn mower. You might think that since the lawn mower runs on fuel, higher fuel delivery should be the way to go.

This brings back memories of my first lawn mower. I was sure that the higher the concentration in the fuel store, the more the speed of the lawn mower would be determined. I was wrong.

My actions caused the mower motor to run rough. It can even lead to permanent damage to the carburetor in rare cases. If the fuel supply is overwhelming, the carburetor can leak.

If the carburetor is leaking without your knowledge, think of the potential damage it could cause. This is why you need to know the role of a choke in your lawn mower.

The same applies to the air flow in the carburetor. Cutting off the air supply can also cause the engine to stop working as it was manufactured.

If you notice and feel any irregularities in the idling or normal operating sound of your mower after ruling out choke positioning, I recommend that you get your little engine mechanic to take a quick look.

When the choke lever is pushed up the choke is engaged and when it is pulled down it disengages. You can also pull the lever halfway down during operation or halfway up at the beginning of operation. The colder the engine, the more fuel it needs and the higher the lever should go.

If you’ve determined that none of these positions cure sputtering or stalling, it’s time to look elsewhere for the solution.

The final touch to the choke-on icon…

To summarize our original question:

The choke-on symbol for most small engines looks like a horizontal ( — ) or diagonal ( / ) line. It can also simply say “Choke”, “Full Choke” or “Start”.

The off symbol for most small motor chokes is represented by a vertical line ( | ) or the word “Run”.

Hope you learned something here. If you enjoyed this article, here are some others you will enjoy…

resources

https://www.wikihow.life/Start-a-Push-Lawnmower

https://faq-law.com/what-does-the-choke-symbol-mean-on-a-honda-lawn-mower/

https://support.troybilt.com/s/article/1947-1?language=en_US

aarrggh!! It’s so annoying. Why can’t you just laze around. Yes, I know the feeling. This is a common ATV complaint.

An ATV that dies when the choke is pulled off is symptomatic of a dirty pilot jet in the carburetor. Removing and cleaning the carburetor will fix the problem. Other possible problems are:

Incorrect air/fuel mixture ratio

Faulty carburetor

vacuum leak

This is a common ATV complaint, especially on ATVs that have been idle for a period of time. In this post you will learn why your ATV is only running with the choke and what you can do about it. You’ll also learn how to properly adjust the air/fuel mixture and we’ll cover the basics of air/fuel ratio.

This post is about carburetor engines. If your bike is fuel-injected, stalling at idle can be caused by several components, including the injector, airflow meter (if equipped), TPS, intake temperature sensor, etc. The best place to start diagnosing a fuel-injected bike should be reading the ECU fault codes and checking the gas quality, air filter and spark plug.

We’ll look at the importance of the air-fuel ratio first, as it’s helpful to have an overview of what’s going on. However, if you want to dive into the basics of repairing, jump to cleaning the pilot jet here.

What is Air to Fuel Ratio (AFR)

The simplest solution to this problem may be a quick air/fuel mixture screw adjustment, and you can read all about it here. However, as you will find, the customization is often not the cause of the problem.

Your ATV requires an air to fuel ratio of 14.7 parts air to 1 part gas. Any variation of this ratio and the engine is referred to as “running lean” or “running rich”.

A lean condition can cause your engine to overheat, and a rich condition can wash out the cylinder’s protective oil coating and dilute the engine oil.

Both of these conditions will cause your engine to run poorly and should be addressed as soon as possible. If both conditions are neglected, there is a risk that your ATV’s engine will fail.

lean condition

A lean condition is a lack of gas relative to the volume of air an engine is receiving. Any ratio above 14.7 parts air to 1 part gasoline is a lean condition.

Causes of Lean Condition – A lean condition can be caused by either too little gas in the combustor mixture or too much air.

Not enough gas in the mixture is easy to imagine, a fuel lock or a bad mixture setting, but how could there be too much air in the mixture?

Because your carburetor is under vacuum, the engine draws in air from wherever it can get it. A damaged carburetor mounting gasket or manifold is letting in undated air. A vacuum leak around the air/fuel mixture screw is also possible.

On the mechanical side, a damaged head gasket, valve timing, or damaged valve seats will allow undosed air into the combustion chamber, creating a lean condition.

If air does not flow through the carburetor inlet (venturi), it will not be mixed proportionally.

Lean condition symptoms – These can vary, the most common are:

Not starting

Start and die

Runs with choke only

Engine jerks, engine runs irregularly

Engine cuts out when accelerating

Engine does not idle

engine speed high

Engine running very hot

White spark plug

Engine misfire

rich state

A rich condition means that there is too much gas in the combustion chamber relative to the air. Any ratio below 14.7 parts air to 1 part gasoline is a rich condition.

Causes of a Rich Condition – A rich condition can be caused by either too much gas in the mixture or not enough air. Common causes of a rich condition are an adjusted air/fuel mixture screw, a faulty carburetor, a faulty carburetor needle seal, a dirty air filter, an air box or line blockage.

Symptoms of Abundant Conditions – Symptoms vary, the most common are:

ATV stinks of gas when starting

Engine floods easily

Black smoke comes out of the tailpipe

Oil level higher than the full mark

Black plug

Engine misfire

Adjusting the air-fuel ratio

AFR can be adjusted and must be adjusted as carburetor and engine wear. Carburetors are factory adjusted and some may even have a tamper evident screw to prevent adjustment or major adjustment variations. As you know, incorrect adjustment can damage your engine.

Most carburetors have two adjustment screws, an idle speed screw and the air/fuel mixture screw.

The idle screw controls the idle speed of the engine. It just opens the throttle. Think of it as a doorstop. It has no other function. It may be part of the throttle cable on some carburetors.

The air/fuel mixture screw is the business end of carburetor mixture adjustment. The screw (usually a brass pan head) is accessible as it needs to be adjusted while the engine is running.

Adjusting the AFR is as follows:

The engine should be warm

Go ahead and locate the brass mixing screw and turn it all the way in (clockwise) until it is seated. Do not tighten it as it is a delicate screw that could break.

Now unscrew the screw by a quarter turn.

Start the engine and try to idle the engine, turn the screw further out (counterclockwise) until the engine idles.

Now accelerate hard: If the engine stalls (hesitates), turn the screw further out until this no longer occurs. Once you find that sweet spot, open the screw an additional 1/8 turn. If, on the other hand, the engine does not jerk when accelerating after the initial adjustment: Turn the screw in far enough, then turn the screw back out in small steps until it stops, then finally turn it out another 1/8 turn.

You may need to adjust the idle screw afterwards. Turning inward (clockwise) increases speed and counterclockwise decreases. The engine should idle smoothly and not be difficult to shift (manual transmission).

If that didn’t work, go ahead and clean the pilot circuit.

Dirty carb causes lean condition

Since your ATV is only running with the choke, it means your engine is running too lean. If adjusting the AFR didn’t solve the problem, the lean condition is most likely caused by a dirty fuel nozzle and specifically the pilot nozzle.

Carburetors commonly use three (some more) fuel jets responsible for supplying gas to fuel circuits, which in turn are activated by various throttle requirements.

When diagnosing gas problems, it helps to know which circuit controls what:

Idle and stumble issues at 1/4 throttle (our problem) – check the pilot circuit as it is responsible for the throttle feed from idle to 1/4 throttle. First try adjusting the fuel mixing screw.

Stumbling at 1/4 to 3/4 throttle – check that the needle jet is clean and try adjusting the position of the clip.

Stumbling from 3/4 to full – check that the main jet is clean and consider turning the carb down (especially if it had some engine mods).

The engine stalls with a click of the accelerator pedal – Check the accel pump, timing and leak jet operation.

And so, in this area, the needle jet moves from 1/4 to 3/4 throttle and the main jet is responsible for 3/4 to full throttle.

The partially blocked pilot jet (idle jet) reduces the amount of gas fed to the engine at idle, which in turn causes it to stumble and stall.

Applying the choke will reduce the volume of air entering the engine, adjusting the ratio closer to 14.7 to 1 and allowing your engine to run smoothly again, but this is obviously not a viable solution.

The solution, as you know, is to clean the pilot jet. But just before we do that, let’s check two easy-to-check critical components that can also cause idle issues. Gas quality and spark plug.

bad gas

Gas becomes old, and mixed gas may become old after about a month under certain storage conditions. Stale gas loses its ZING and your engine may have trouble running and may lack power. If your gasoline is old, drain the tank, carburetor chamber and refuel.

Carburetor gumming is the next level of stale gas and is a real problem, especially on ATVs that are layed down over the winter.

The spent gas in the carburetor body eventually vaporizes, leaving a sticky gel that clogs the carburetor’s main jet. This is a condition that affects all small motor kits, from ATVs to mowers.

If your ATV has been idling for some time, there is a greater chance that gumming is causing your problem. The only solution is to remove the carburetor and clean it thoroughly with carburetor cleaner or in an ultrasonic cleaning tank.

However, gumming can be prevented, you can use a gas stabilizer in the fuel during storage. A stabilizer keeps the gas fresh for up to a year. A full gas tank also helps prevent moisture build-up.

spark plug

Your spark plug is critical to how well your engine runs and is at the top of any list of problematic gas engines. The symptoms of a faulty or incorrect spark plug are so varied that I’ve learned to eliminate them early in the diagnostic process. The verification takes a few moments and can save you a lot of time.

Your engine manufacturer will specify a specific spark plug by code, we need to ensure the correct plug is fitted. Spark plugs are classified by heat and the most important thing is that a spark plug gets just hot enough to burn off impurities but not so hot that it causes pre-ignition. Incorrect heat range will cause problems.

Unplug and read condition: Tan insulation – a healthy plug

Black plug – runs full

White plug – runs lean

Oily plug – mechanical problem

With the connector removed, check and clean the gap.

Use a feeler gauge to check the gap.

Remove and clean the pilot jet

After these have been checked, we can now devote ourselves to cleaning the pilot circuit. It may be necessary to remove the carburetor to clean the pilot jet. Some carburetors are easier to remove than others. On some models it is possible to remove the jet without removing the carburetor.

To do this, you need space to work under the carburetor. So if you have room, turn off the fuel tap and remove the fuel pan. The bowl lives at the base of the carburetor and is a fuel reservoir that stands by to feed the jet.

Sand that passes through the gas filter usually hides in the bottom of the bowl. Most bowls come with a drain plug, useful for maintenance. It’s worth emptying the fuel bowl, it often fixes bad running problems.

Bowl Bolts – The bowl is attached to the carburetor, usually 2 or 4 bolts. Here you need the space we talked about earlier to work with the screwdriver. A short-handled butty screwdriver and bit set are the ideal tools for this job. Make sure your driver is an exact fit. These screws are often damaged and can be difficult to remove when the carburetor is on the engine.

Gas Tap – Your gas tap must be in the off position as gas will flow as soon as you remove the bowl. You can find your petcock by following the gas line between the tank and the carburetor. The faucet will be marked as on and off. If you can’t find it, don’t worry. Use a fuel line clamp or small vise to gently pinch the line.

Bowl Gasket – With the bowl removed, you may find a rubber bowl gasket on the bowl or carburetor side. If it is present it is best to leave it there, these types can expand when removed and can be difficult to reinstall properly, especially if the carburetor is on the engine.

Rinse the bowl out with some carburetor cleaner and set aside.

Needle Seal – The plastic/metal float and needle control the flow of gas to the bowl. Removing the float pin releases the float and needle. The needle is small, so I lay out a shop towel to catch it.

A faulty needle valve or incorrect float height can cause fuel starvation. Needle seals are wearing parts and can be replaced. The rubber seal often turns pink when old and worn.

Pilot Jet – We want to locate the pilot jet as it is the fuel circuit that is most likely to cause an idle problem. Still, it makes sense to remove and clean all the jets while we’re in here.

Main Jet – The main jet is not as impressive as its name might suggest. Jets are made of brass and resemble a small hollowed out screw.

You’ll need your butty driver and bit set again, brass resists corrosion and that’s great for a carburetor, but brass is a soft metal and an ill-fitting screwdriver can easily dislodge the jet head. A correct fit is mission-critical here.

The jet can be cleaned with a wire brush and some aerosol carburetor cleaner. The screw hole must be clean.

Needle Nozzle/Emulsion Tube – The emulsion tube is also made of brass. Not every carb will have one. It depends on the carbohydrate type. The pipe uses several carefully calibrated portholes in the wall, all of which supply gas to the engine.

Over time, these holes get smaller as microscopic grains get stuck on the edges. This may not be obvious at first glance, but if you clean a porthole you will see the difference.

The size of the portholes in the nozzle and tube are important as they are calibrated to match the size of your engine. Use some carburetor cleaner and a strand from a wire brush or a strand of copper wire from an electrical wire. Using a more abrasive tool like a micro-drill will make the portholes larger, which will negatively impact AFR.

Reassemble your carburetor in reverse order, turn on your gas and check for gas leaks before starting and testing.

Faulty carburetor

A faulty carburetor is also common, don’t rule it out. They are precisely calibrated pieces of kit and will wear out. Unfortunately, you probably can’t tell if a carburetor is bad just by looking at it.

But once you’ve gotten rid of bad gas, dirty carburetors, fuel delivery problems, vacuum leaks, and mechanical problems like head gasket valve leaks, swap it out for a new one.

related questions

Is it harmful to run an engine with the choke on? Yes, operating an ATV with the choke on runs the risk of excess gas washing the protective engine oil out of the cylinder. The gas travels to the crankcase and dilutes the engine oil.

You might find the following posts useful:

ATV carburetor leaking

ATV Carburetor Flood

Dwight Coleman there are usually only a few options if it only runs with a choke. One cause could be an air leak at the carburetor, head gasket, and crankshaft seal. The other could be a clogged circuit at low RPM and idle. Since you just finished the engine, I would check the carburetor again. You want to make sure it’s properly adjusted and clean. Double check everything and check for air leaks.

Aragh I know the feeling. There is never a good time for a mechanical failure. Don’t worry, we’ll find out.

The top 4 reasons why an ATV dies when you give it gas:

Too little gas (clogged main jet) Too much gas Ignition failure Clogged muffler

In this post, you will learn about the most likely causes of ATV stalling and what you can do to fix them.

In my experience, three common faults cause this condition: dirty main fuel jet, improper fuel mixture setting, and incorrect needle clip position. We will cover all of these and other possibilities in this post.

Overview of the fuel system

Most stalling problems are caused by a tank problem, either too little or too much. Before we delve into your issue, it may be helpful to have an overview of how an ATV fuel system works and the preferred fuel ratio.

Fuel Injected Fuel Systems – Some modern ATVs use ECU controlled fuel injected fuel systems. This guide does not cover these types of models. If you have a fuel injected system, start your diagnosis by reading DTCs. (Diagnostic Trouble Codes).

A common cause of a fuel injected bike eating when you give it gas is a throttle position sensor fault and fuel injection problem. Check that the cable clamps are secure and undamaged.

Fuel Injected Bike Shop Trouble Codes and this is the smartest place to start diagnosing.

Carburetor Fuel Systems – Since most ATVs are equipped with carburetor fuel systems, this guide will cover them.

Your ATV carburetor is a precision part of the kit and has three distinct jobs.

Mix air and gas in an exact ratio. Deliver the right amount for the specific engine load. Have an adequate supply of gas ready

Gas engines happily run at an air to fuel ratio (AFR) of 14.7 parts air to one part gasoline. This is the optimal ratio and is referred to as “stoichiometric”. When a technician tunes your carburetor, this is the ratio they are tracking. As you will learn, many things affect AFR, most of which can be controlled by the driver, but some cannot.

diagnosis

In most cases, cleaning the main jet will fix your problem, but it doesn’t hurt to run a few quick tests first to confirm our suspicions.

Question 1:

Does your condition improve when you operate the choke lever? If this is the case, you have a lean condition. See adjusting your carburetor below.

Question 2:

Does removing the air filter help? If so, your engine is running rich. See Adjusting the Carburetor below.

Question 3:

Does the engine only die when you accelerate quickly? If this is the case, your accelerator pump may need to be checked. See Accelerator Pump Adjustment below.

Question 4:

Does your engine stall when you hit the gas both fast and slow? If this is the case, your main jet may be clogged. You will need to disassemble and clean your carburetor.

Question 5:

What is the condition of the spark plug? A black candle indicates a rich running engine and a grey/white candle indicates a lean condition.

Question 6:

Did you make modifications like a bigger air filter or exhaust, or an altitude or temperature change? These types of changes require fuel adjustment and possibly a carburetor re-jetting.

All diagnostics should begin with fresh gas in the tank and a clean air filter. You should also know that clogged carburetor jets cause most running problems. It never hurts to thoroughly disassemble and clean the carburetor.

The answers to the above questions will put you on the right path.

run lean

When your engine isn’t getting enough fuel relative to air, it’s called lean running. Or to put it another way – the engine gets too much air.

Symptoms of a lean engine vary depending on how lean it is running, but here are some of the most common:

Hanging idle

Vary

swamp

stall

To pop

Starts and dies

Runs with choke only

Dies when hitting the gas

The causes of a lean engine are just as diverse. Here is a list of the most common ones and the solution:

Cold ambient temperatures or higher altitudes – adjust the mixture

Mixture not set correctly – adjust mixture

Old gas – replace with fresh gas

Blocked carburetor jets – remove and clean carburetor

Low fuel level in tank – adjust float

Engine Modifications – Modifications such as larger air cleaners or fast-flowing exhaust systems will likely require a carburetor re-blowout

Vacuum Leak – Check carburetor bolts for tightness and carburetor gaskets and manifold for leaks

Fuel pump defective – Check fuel flow

Valve clearance out of specification – adjust

accelerator pump

A very common cause of throttle stalling is an accelerator pump failure. The pump is only used when you step on the gas from idle. Its purpose is to inject a shot of gas into the carb that helps counteract the lean condition caused by the airflow when you open the throttle wide.

How does it work? The system uses two main components:

Pump leakage nozzle

The pump consists of a rubber diaphragm, a fuel port and an adjustable cam. When activated, the throttle assembly pushes on the pump cam, causing the diaphragm to shoot gas through an orifice facing the venturi. (Note that not all systems work exactly this way, but this type is typical.)

Adjusting the point of contact between the throttle and pump cam affects the timing and duration of the throttle burst. A good gas burst should last about a second and be timed to barely miss the slide when it opens.

When the gas shot hits the slide, its effectiveness is reduced. You need to set the camera so that the shot arrives shortly after the slide is raised. Although I’ve shown the AP here on a CV-type carburetor, it’s really only found on a mechanical slide carburetor.

Problems with the pump include:

time out

Worn membrane

You can check the operation of your pump by removing the suction line and quickly flicking the throttle and observing the burst of gas.

The leakage jet removes gas when it is not needed by the pump. When the throttle valve is slowly opened, the gas simply flows back through the leakage nozzle into the carburetor chamber.

The amount of gas delivered by the pump is directly affected by the size of the leakage jet. A smaller leak jet delivers more gas to the pump and a larger leak jet reduces the gas volume to the pump.

Problems with the leak jet include:

Incorrect sizing

blockages

The amount of gas delivered by the accelerator pump is directly influenced by the time, duration and the built-in leakage nozzle. You can rule this out as a possible cause by slowly opening the throttle. If the problem isn’t there, your accelerator pump needs attention. If the problem persists, try adjusting the carburetor. See below.

run rich

Your engine is said to be running rich (aka rich) when it is receiving too much fuel in relation to the volume of air it is receiving. Or to put it another way – your engine is not getting enough air.

Symptoms of a rich running engine include:

swamp

stall

misfire

Black smoke

misfire

Wet plug

Black plug

Common causes of a rich running engine are:

Mix out the setting – adjust

Dirty air filter – clean or replace

Float needle leaking – replace

High float level in the pool – adjust

Faulty petcock – replace

Faulty carburetor – replace

Carburettor injected incorrectly – spray again

Adjusting the carburetor fuel mixture

Adjusting your mix is ​​a little technical, but it’s not brain surgery. Most ATV carburetors have three fuel circuits.

Idle circuit (igniter) – provides gas at light to medium throttle but is solely responsible for idle. 0 to 1/4 throttle

Midrange Circuit (Needle Jet) – delivers throttle between 1/4 to 3/4 throttle

Main circuit (main jet) – supplies gas to the needle jet circuit, from 3/4 to full throttle

A standard setting procedure looks like this –

Step 1

Start with a warm engine. Check how the throttle stick responds across the range. Stop the engine, find your base setting by turning the pilot circuit screw (mixture screw) all the way (clockwise) until it is seated, and count the number of turns. (1.5 to 2 is normal).

Put the screw back in its original position.

step 2

Start the engine and turn the mixing screw clockwise until the engine stops. (Note the amount spun and return after the stand)

step 3

Restart the engine, now turn the screw counter-clockwise until the engine stalls.

step 4

Restart the engine and turn the mixing screw clockwise until the engine speed is at its highest.

step 5

Now reduce the idle screw to a steady idle between 1000-1500 rpm.

If your mixer screw is set more than 2 turns or less than 1 turn after this procedure, this is a strong indication that your carburetor needs to be resprayed.

Your mixing screw is now set correctly. The throttle should respond sharply with no hesitation or swamp.

If it goes wrong, you:

The position of the needle clip may need to be adjusted

Carburetor main jet dirty

The carburetor needs to be re-sprayed

Needle Clip Position

Your needle is at the heart of your carburetor and to access it you must remove it from the bike. The needle moves up and down inside the emulsion tube in response to gas actuation. The higher the needle in the emulsion tube, the more gas the engine gets.

A clip at the top of the needle sets the base height of the needle, it has five positions. The clip is usually adjusted to the 3rd position down. Moving the clip down one position keeps the needle higher and helps deliver more gas (richer). Conversely, moving the clip up thins the mix.

Adjusting the clip position is a trial and error process. A systematic approach works best, as removing and adjusting some carbs can be annoying.

ignition failure

Ignition failure can cause a bike to idle but fail at higher RPMs. Here are some of the checks you can do. Some bikes run without a battery, while others require a strong, fully charged battery. Use a voltmeter and check your battery.

A faulty spark plug, or the wrong type of plug, is a common cause of intermittent performance problems. The best way to check the plug code is by looking in your manual.

Also check if the battery is charging while idle. Anything above 12.65 indicates it is charging. Visually inspect the condition of your plug, cap, plug cord, and coil.

Attach the tester with a simple in-line spark tester and check for spark while accelerating the bike. If the spark fails in the viewing window, you need to check the resistor cap and do a resistance test on the coil, stator and pickup, which is also possible for the CDI box to cause a stalling problem.

The tools I recommend, including an in-line ignition system test, can be found on the ATV tools page here, and common replacement parts can be found on the ATV parts page here.

Clogged exhaust

This is not a very common cause of stalling, but it does happen. The exhaust spark arrestor becomes caked with soot that is so thick that exhaust gases cannot escape and the engine stalls at anything above idle.

With the engine running, hold a shop towel firmly over the exhaust pipe with a gloved hand. Release it after 3-4 seconds. The pressure built up should be great. If it is faint, it indicates a partial blockage.

Go ahead and remove your spark arrestor and clean it.

You might find the following posts helpful:

Why does ATV stall?

Can I drive with a choke?

ATV oil smells like gasoline