Proper chainsaw chain tension is vital for safe and efficient cutting. If the chain is too loose, it may get easily thrown from the guide bar, pinched in the wood and whip back toward your legs. If the chain is too tight, the tip will heat up, your drive sprocket will wear out, your teeth will dull or break and you can even damage the clutch. Each cutting job also requires a different chain tension and only experience will help you get a feel for the proper tension needed to finish the job.
Turn the chainsaw off. Disengage the chain brake. Let the saw cool down before working on it.
Loosen the two bar nuts holding the bar, chain and chain cover in place with the wrench until they’re finger tight.
Locate the bar tensioner screw. This screw is located near the spot where the bar and chain connect to the engine and controls the tension of the chain.
Turn the screw clockwise to tighten the chain and counterclockwise to loosen it. Hold the saw up by the tip. Try pulling the chain away from the bar, near the chain catcher. There should be about seven to nine bottom drive links exposed when the chain is properly tensioned.
Tighten the bar nuts with the wrench. Spin the chain with a gloved hand. The chain should be loose enough so that you don’t need to pull the chain and tight enough that it doesn’t pull off the bar.
Loosen the bar nuts and repeat the process until the chain is properly tensioned.