Chain Saw: Engine Rpm's Too High

Your chainsaw’s carburetor needs to be properly tuned and adjusted to prevent the RPMs from running too high. Fortunately, you can correctly tune your carburetor by adjusting the screws on the side of the carburetor, and set your RPMs correctly. To adjust your carburetor, first turn both adjustment screws in to halt the flow off fuel. Then, turn the screws in the opposite direction 2 turns. Next, start the engine and allow it to reach operating temperature. Turn the L screw clockwise until the engine starts to slow down, then turn it in the opposite direction until it once again starts to slow. Your ideal setting should be at the midpoint of these 2 stopping point. Using a tachometer, set the idle speed screw to bring the engine to 1750 RPM for aluminum-cylinder engines or 1200 RPM for engines with a cast-iron cylinder sleeve. Now, at full throttle, turn the high-speed screw clockwise until the engine begins to slow, then turn it counter clockwise until the engine slows again. The screw will once again want to be set at the midpoint of these stopping points.

Your chainsaw will have a gasket between the carburetor and the cylinder. It is designed to create a seal, which will not allow excess air to enter the cylinder. If the gasket is damaged or leaking, too much air will enter the cylinder, creating a lean condition (too much air relative to the amount of fuel). A lean condition in the cylinder can result in your engine’s RPMs running too high. If the gasket is leaking, missing or damaged, you will need to replace it, so your RPMs return to normal.