Basic Chainsaw Carburetor Mixture Adjustment

This is an informative video off of YouTube that shows the adjustment process for your chainsaw carburetor. Before you start, you should have a clean air filter, and a properly adjusted bar and chain, of the length you will be running. Switching to a different length bar and chain will necessitate a slight readjustment of your high speed mixture, because the load on the engine will be changed.

The idle speed should be adjusted so the chain is stationary when you release the throttle, and you may have to reset that a time or two while changing the idle mixture. If you set the idle too rich, the engine's crankcase will load up with excess fuel, and the engine will flood out when you goose the throttle, or roll the saw into different positions. If you set the idle mix too lean, the engine will stagger when you pull the throttle trigger. Play around with this setting for a while, and you will develop a good feel for setting it right.

The high speed mix should be set so you have a slight burble or miss from just a bit of excess fuel. As you turn the high speed needle leaner, the engine will go to a full scream with no missing. Go a bit further, and you will hear the engine sag. This is very dangerous to your cylinder, piston, and rings, so I don't recommend it, other than to note a reference point during the adjustment. Saws today usually have a cutout in the coil circuit that causes the engine to stutter when it is being over-revved, so be careful not to confuse that with the slight miss from a rich mixture.

The fellow in the video has a tachometer, which is pretty handy to have, but it is not necessary. It is more important that you learn to recognize the notes of an engine that is running rich, lean, and at a slightly rich and safe mixture.