Whether you ride your motorcycle to work every day or for long distances, nothing is more frustrating than having the engine stall when given throttle. But why does this happen?
When the ratio of air to fuel is too high or too low, the motorcycle will die when you give it throttle. This loss of power can also be caused by a dirty air filter, worn ignition system, or clogged carburetor jets, among others.
There are several things that could be causing your bike’s stalling while the clutch is engaged or disengaged, regardless of whether it is carbureted or fuel-injected. We’ve compiled a list of the top 10 reasons behind this below.
1. Dirty Air Filter
If your motorcycle was previously running smoothly but now stalls whenever you apply the throttle, the air filter is likely the culprit. That’s why it’s the first thing to check. When an air filter gets dirty, it can clog up to the point where it hardly lets clean air through to the intake manifold or carburetor.
There isn’t much airflow required at closed throttle, so your bike can start and idle just fine. Then, the motorcycle dies with a wide open throttle since it requires additional gasoline and air.
2. Old and Faulty Ignition System
Failure to routinely inspect and repair your motorcycle’s ignition system might cause the ignition spark to deteriorate to the point where the bike stalls when accelerating. That’s why you need to inspect the state of your bike’s spark plugs. As its name suggests, the spark plug is responsible for igniting the fuel-air mixture in an internal combustion engine.
This means that if you have a bad spark plug, the entire motorcycle’s ignition system is compromised. A motorcycle’s spark plugs need to be checked at the maintenance intervals recommended by the manufacturer’s service manual and each time the engine stops when the throttle is applied.
You might need to get a new spark plug.
3. Clogged Carburetor
The pilot and main jets in your carburetor have tiny openings that can be easily blocked by dirt. This could be the case if your bike has a damaged air filter or the carburetor has been opened recently. You might be able to get the bike to idle with a partially plugged pilot jet or main jet, but it might die if you try to add more fuel by increasing the throttle.
When the throttle is closed, the pilot jet feeds the fuel. The pilot jet may be partially clogged if the motorcycle starts and idles but stalls as soon as you apply the throttle. On the other hand, the main jet is likely the problem if the bike accelerates smoothly at low throttle settings but sputters or dies when given full throttle. Using a carb cleaner to clean the intake and clogged jet is the easiest way to address this.
4. Loose Throttle Cable
The carburetor’s butterfly valve won’t open fully, and the engine won’t get enough fuel and air if the throttle cable is too loose. Even if the engine doesn’t die, your motorcycle will seem to have less power than usual whenever you try to speed up.
As long as the pilot jets are feeding fuel, the motorcycle should start and idle normally, even with the throttle closed. When the clutch is released too quickly, the engine might stall because the fuel line supply cannot counteract the motorcycle’s weight.
5. Vacuum Leak
Any air leaks between the carburetor and the engine will cause an unsuitable air-to-fuel ratio. The function of the carburetor is to pump out the proper ratio of air and fuel for the engine’s internal combustion process. As air is sucked in through a vacuum leak, it dilutes the air-to-fuel mixture, making it difficult to ignite. Increasing the throttle will cause a greater air intake.
Inspect the intake boots connecting the carburetor to the engine’s manifold for tears and tighten any slack clamps. The vacuum lines should be in good shape and not disconnected from the carburetor chamber. Testing the carb by plugging the hole where the vacuum hose would typically attach to it, if you find that it isn’t working, is a good idea.
6. Clogged Fuel Filter
If the fuel filter is so dirty that the flow of fuel is reduced, the engine may have just enough power to idle but not enough to move forward. A blocked fuel filter is usually the result of rust or sediment in the fuel tank. If the fuel filter is clogged, you should be able to fix the problem by installing a new filter.
On the other hand, inline fuel filters are not common on bikes that have carburetors. In its place, a mesh filter is installed in the fuel tank petcock. Simply unscrew the petcock to clean the filter. If your motorcycle does not already have one, you should place an inline fuel filter between the carburetor and the fuel tank.
7. Disengaged Choke Lever
If your motorcycle suddenly stops working after you give it some throttle, an open choke could be to blame. Most typically, this occurs after a bike is started with a cold engine or after being parked for an extended period.
To make sure the choke is fully open, check it. If adjusting the choke lever doesn’t really affect the idle speed of the engine, the cable may be damaged or need adjustment.
In addition, leaving the gasoline cap off for a long time may wreak havoc on the motorcycle’s air screw, spark plug, combustion chamber, and throttle cable, resulting in a loss of power. If this is the issue, the simple fix is running the motorcycle at high idle speeds and progressively increasing the air-to-fuel mixture until the choke stops working.
8. Insufficient Compression Level
As you apply throttle to speed up, your motorcycle’s engine might stall because of a lack of compression. If the piston rings are worn out, motorcycle engines might shut down if the compression level drops below a safe level. A compression test can help you verify whether this is the issue.
You must first identify and remove the faulty gasket or seal to repair the damaged compression. Remove the motorcycle’s engine cover to access the malfunctioning components and replace them. Or, the problem can be solved by using a good ratio of high-quality two-stroke oil.
9. Clogged Fuel Cap Vent
When the outlet in your gasoline tank’s filler cap is clogged, this will produce a vacuum inside the fuel system, which prevents the flow of fuel. When fuel is drawn into the carburetor or pushed to the fuel injectors, the pressure in the tank rises; thus, an air vent lets outside air in to bring it back to normal.
Check the gas cap’s vent hole carefully and remove any debris blocking it with a wire if necessary. If this does not work, the fuel tank cap needs to be replaced.
10. The Motorcycle’s Fuel System Has Water in It
Water can enter your bike’s gasoline supply through tank leaks or the accumulation of compensation after prolonged cold-weather storage. Water leaves the fuel tank first and settles to the bottom of the carburetor float bowl because it weighs more than the fuel. You could get the bike started and idling without any problems, but once you give it more gas, it might sputter and die.
If you fill your bike’s gas tank all the way up before putting it away, you won’t have to worry about moisture in the fuel, causing it to stall once you hit the gas. You can also solve this issue by removing the drain screw from the float bowl’s base and emptying the water that has been collected there.
It can be frustrating when your bike has an excellent idle but dies as soon as you give it any gas, but the problem is typically easy to fix. Now that you have a better knowledge of what might be causing your motorcycle to stall when you apply the throttle, you can take steps to address the problem. If you understand why these things happen, you won’t have to freak out the next time they do, especially if this is your first bike.