Blower: Engine Rpm's Too High

The fan on your blower is also known as an impeller and spins to draw air into the blower. The air that is pulled in through the side of the housing by the fan, is directed to the front of the blower through the blower tube. If several of the blades of the fan are broken off, it can cause the engine’s RPM to increase. During the life of your blower, debris can inadvertently be drawn into the fan blades, and this can cause them to break. Be sure to clear out any debris that enters the blower housing to help avoid this issue.

The carburetor in your leaf blower ensures the proper mix of fuel and air is entering your engine. When the carburetor is damaged, it can cause the engine to run lean, which means too much air is entering the engine. Too much air in the engine will cause the engine RPMs to run too high. This can be a serious issue and can lead to damage to the cylinder or piston, ultimately leading to complete engine failure.

The carburetor for your leaf blower may also be improperly adjusted. To re-adjust the carburetor, you need to locate both idle screws. One will be marked L (low) and one is marked H (high). To begin the adjustment, first turn both screws all the way in to shut off the fuel. Next, turn the screws in the opposite direction for 2 turns. At this time, you will need to start the engine, and allow it to idle for a few minutes. Now, turn the L screw clockwise until the engine starts to slow, then turn it in the opposite direction until it once again starts to slow. The ideal setting for the screw will then be the midpoint of these two stopping points. Next, use a tachometer to gauge engine speed, and set the idle speed screw to bring the engine to 1750 RPM for aluminum-cylinder engine or 1200 RPM for an engine with a cast-iron cylinder sleeve. Then, at full throttle, turn the high speed or main jet screw clockwise until the engine begins to slow. Turn the screw in the opposite direction until the engine begins to slow. Once again, you will want to set the screw at the midpoint of these two points. Once adjusted, check the engine acceleration by moving the throttle from idle to fast.

The impeller is critical to the proper function of your leaf blower. Also known as a fan, the impeller rotates to draw air in, at which time it is redirected through the blower tube. A broken impeller, which is normally caused by debris entering the blower housing and damaging the fan blades, can result in your engine RPM running too high. Be sure to keep the blower housing clear of debris to reduce the likelihood of your impeller blades breaking.

If you have a large, wheeled blower with a 4-cycle engine, you will have a rod that links the throttle control to the governor arm. The governor is designed to regulate the speed of the engine regardless of conditions. The governor will increase the throttle in tougher conditions to maintain the speed. If the rod that connects the governor to the throttle becomes loose, or is damaged, it will not allow the governor to control the throttle. This can result in your engine RPMs running too high.

A large, wheeled blower with a 4-cycle engine could have a damaged or incorrectly set governor. The governor in your leaf blower is designed to maintain a desired speed. It works in conjunction with the throttle to control the that speed. If your governor is incorrectly set, it can cause your engine RPMs to run too high. A damaged governor or governor arm can result in higher-than-normal engine RPMs as well.