Why Leaf Blowers Bog Down at Full Throttle

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Does your leaf blower suddenly bog down when you go full throttle? It runs fine when idling but you switch it up everything comes to a halt. This can be frustrating especially when there is a lot of work to be done. But no worries as we have compiled a list of reasons and solutions.

A leaf blower usually bogs down when the air filter is clogged with dirt. Without enough air, the system is unable to run at full throttle. This can be fixed by cleaning or replacing the filter.

There are other reasons why a leaf blower can bog down and those will be covered in the rest of this article. Without further ado, let us go over these problems and solutions.

Blocked Air Filter

There are two things that can slow down or damage a leaf blower engine, heat and dirt. An air filter is designed to minimize both, so it is important that you keep the filter clean. If the air filter is too dirty, replace it with a new one.

Because of the way engines work it gets hot. An air filter allows air to cool the engine so it does not overheat. When you run a leaf blower at full throttle, the engine exerts more pressure and gets hotter. This forces the air filter to work harder. And if it is covered with dirt, the blower might stall.


Turn the leaf blower off and take the filter cover off. If the leaf blower is heavily used, the air filter will likely be covered with dirt and debris. Replace the filter if there is a rip or any damage. But if there is only dirt, you may clean it with warm, soapy water.

Put the filter back on after it dries. Keep in mind that air filters for the Craftsman B235 and others should be replaced after one year for the best results. There are a lot of these available and they are also inexpensive.

Faulty Spark Plugs

Next to the air filter, the spark plug is the most likely to need cleaning or replacement. Like other power tools, a leaf blower engine depends on the spark plug to run.

A dirty or faulty spark plug prevents the engine from using fuel efficiently. Couple this with old fuel and your leaf blower will encounter problems operating at full throttle.


If you suspect the spark plug is the problem, use a spark plug tester like the one by Lisle. This will tell you if it is defective or not Before you run the tester, clean the spark plug. Carefully remove it and wipe away the dirt and carbon deposits.

If the spark plug is covered with old gummy fuel, you have to check the rest of the engine too. Drain the old fuel and wipe away any residue on the engine before adding new gas.

If you cleaned the spark plug and it works during the test, it is still usable. If it fails the test, get a new one. Refer to your leaf blower manufacturer website for compatible spark plugs.

Spark Arrestor Problems

The spark arrestor prevents flammable materials from getting out of the engine; All 2-stroke leaf blowers have this feature for good reasons.. Spark arrestors work like filters, and they also accumulate dirt through constant use. This can also be the reason why your leaf blower is not blowing hard enough, though there are other possible causes as well.


The spark arrestor has to be cleaned after every 50 hours. Remove the spark arrestor and use a wire brush to remove the debris. Cleaning should work as long as the spark arrestor has not been damaged. If there are cracks however, you should replace it with a new one.

This video shows you how to replace a spark arrestor. The leaf blower here is from Echo, but the basic process is the same for other brands and manufacturers.

Defective Rewind Spring

Leaf blowers have a starter cord or rope which gets pulled and let go. This enables the rewind spring to recoil the cord into the pulley. If the spring is broken or worn out, the leaf blower might have trouble running when set at full throttle.


There are two options, replace the spring or the whole recoil starter. I5 is cheaper to replace the spring only, but getting a new recoil starter is a good idea if the blower is old. Buying a replacement part is easy, but make sure that the component is compatible with your blower.

Clogged Fuel Filter

The fuel filter prevents debris and contaminants from getting into the engine. A poorly maintained fuel reservoir might contain impurities stemming from old fuel, dirt etc. The fuel filter screens these out and make sure they do not reach the fuel line and engine.

If fuel is left in the tank for several months, it will turn into a gummy substance. This residue can clog the filter and prevent fuel from reaching the engine. Without enough fuel, your leaf blower will not have enough power to run. if not fixed, the engine eventually ceases to run.


If you have replaced the fuel filter and the blower still struggles at full throttle, it could be due to the fuel filter. Follow these steps to fix the problem.

  1. Get a new fuel filter as clogged ones cannot be reused.
  2. Turn of the leaf blower.
  3. Empty the fuel tank.
  4. Clean the fuel tank. Check the rest of the engine for old fuel residue and clean it
  5. Disconnect the spark plug and fuel line. This is straightforward, but check your leaf blower to be sure.
  6. Take out the fuel filter. The process may vary depending on the leaf blower.
  7. Install the new fuel filter.
  8. Reconnect the spark plug fuel line and other parts you took out Install them in the reverse order you took each one out.

Just like spark plugs and air filters, fuel filters should be replaced once a year. It also helps to use quality fuel to prevent the filter form getting too clogged.

Carburetor Troubles

The carburetor is the part that mixes air and fuel so the spark plug can ignite it. For this to work the carburetor must provide the right balance of air and fuel.

if the air filter is clogged, the mix will lack air and becomes too rich. If the fuel filter is dirty or damaged, not enough fuel will get in, causing the mix to become too lean.

If the fuel filter or air filter is clogged up, the carburetor cannot mix the fuel correctly. This can result in all kinds of problems such as lack of power.


The fix depends on what type of problem the carburetor has. The following are some suggestions.

  • Dirty air filter. Clean or replace the air filter.
  • Clogged fuel filter. Replace the fuel filter.
  • Damaged carburetor. If there are cracks or any other sign of damage, the carburetor has to be replaced. It cannot be repaired.
  • Clogged carburetor. This is usually caused by old, sticky fuel. A carburetor cleaner is all you need to remove the old fuel.
  • Adjustment. If you have done all these and the leaf blower still won’t run on throttle, change the adjustment /screws. There are two screws for low and high speed. Adjust the screws until the engine is running smoothly.

Old Fuel

A lot of problems with leaf blower engines stem from old fuel left in the reservoir. Gas left over for months will evaporate and turn sticky. When that happens the carburetor does not get enough fuel to power the engine.

The longer you keep old, sticky gas in the tank the more it can spread. When it reaches the air filter, air gets blocked out When the residues makes ti to the fuel filter, the spark plug and other components the engine might completely stall.


Replace the old fuel. Empty the fuel tank, clean the residue and pour a new mix. Replace the fuel every four weeks. Remove the fuel if you are going to store the leaf blower for the winter.