Chain Tensioning: The #1 Chainsaw Maintenance Mistake
A chain that is too tight destroys your bar and sprocket. A chain that is too loose jumps off and causes kickback. Here is exactly how to tension a STIHL chain correctly every time.
Why Tension Matters
The chain on a STIHL chainsaw must be tight enough to drive the cutters through wood efficiently, but loose enough to rotate freely around the bar without binding. An overtightened chain creates excessive friction against the bar rails, overheating the bar, burning out the sprocket, and stretching the drive links prematurely. You will know a chain is too tight when the saw smokes during idle or the engine labors even in soft wood.
An undertightened chain is equally dangerous. Loose chains can derail from the bar during cutting, whipping back toward the operator or wrapping around the clutch housing. A derailed chain often damages the drive links beyond repair and can score the bar rails. The scariest scenario is a loose chain climbing over the bar nose during a top cut, which can cause sudden violent kickback.
The Proper Tension Test
STIHL recommends the snap test as the most reliable tension check method. With the engine off and chain brake disengaged, lift the chain at the center of the bar with your gloved fingers or a flat screwdriver. The drive links should rise partially out of the bar groove but still remain engaged. When you release the chain, it should snap back into the groove with an audible click. If it hangs loose or sags below the bar, it is too loose. If you cannot pull it out of the groove at all, it is too tight.
Always check tension when the chain is cold. A hot chain expands and appears looser than it actually is. If you adjust tension after a long cutting session, the chain will be overtightened when it cools. Check cold tension before every use, and retighten after the first tank of fuel as the chain beds in on a new bar.
Adjustment Procedure
Start by loosening the bar nuts slightly — just enough that the bar can slide forward and back but the nuts still hold the cover in place. Locate the tensioning screw, which sits either on the front of the saw body or at the base of the bar depending on your model. Turn the screw clockwise to tighten or counterclockwise to loosen, watching the chain position as you adjust.
Once the snap test indicates correct tension, lift the nose of the bar with one hand while tightening the bar nuts with the other. This step is critical because tightening the nuts without lifting the bar allows the bar to settle backward, immediately loosening the chain. After the nuts are tight, spin the chain by hand to confirm it moves freely. Start the saw briefly at idle and listen for any grinding or dragging sounds that indicate residual overtightening.