How to Adjust Chainsaw Tension
A good chainsaw can last you a lifetime, but only if you take good care of it. A properly adjusted chain is safer, more effective, and longer-lasting, and this is one small maintenance task that you can do easily at home.
1. **Ensure the ignition switch is off and remove the spark plug wire to ensure the blade cannot start.** This is the small cap, often on the button you use to prime the chainsaw. Disconnect it so that the motor cannot get the electricity required to start.
2. **Wear thick safety gloves at all times when touching the blade.** This is not only for your safety but also for the health of the blade. Granted, touching it once or twice won't kill it, but it is better for both you and the chainsaw if you keep gloves on at all times.
3. **Tighten your chainsaw blade when the chain no longer sits flush on the guide bar.** The bar is the long "knife" of the chainsaw -- the part you use to guide the blade and actually cut. The chain should wrap snugly around the whole bar, not be hanging off the bottom side. If it is hanging, you'll need to adjust the tension.


 Wearing gloves and goggles, hold onto the top of the saw. With the other hand, lift the chain off the bar (near the mid-point of the bar) slightly and let go. If it doesn't snap back into place cleanly, you'll need to adjust the tension.
For precise work, you want about a 1.25mm space between the blade and the bottom of the bar when the motor is cool. A hot motor and chain will slightly expand the chain, loosening it slightly.
4. **Remove or loosen the covering where the blade meets the motor.** For older models, this cover likely comes right off. For newer ones, there may be two screws or nuts holding it down. At the very least, loosen these two screws or nuts a full turn so that the blade and chain have room to shift as you adjust the tension.
Some smaller saws may have a knob or lever to release the cover, instead of screws or nuts, making it easier to adjust without tools.
5. **Clean out the engine and drive-train with compressed air and a rag.** If the cover comes all the way off, use this chance to wipe down the entire assembly, assuring the blade runs cleanly without unnecessary friction. Otherwise, get a can of compressed air and shoot it into the loosened covering to remove dirt and dust.
A toothbrush is a good way to help remove tricky, hard-to-reach bits.
6. **Add a touch of grease to the rolling tip at the end of the blade.** This sprocket is vital to keep the blade moving efficiently. Add a touch of grease so that it can spin freely, and then wipe up any excess with a dirty rag.

Not all guide bars include a roller tip and not all roller tips require additional grease. Follow the operating instructions for your particular saw.
 If you're adding a new chain and want to adjust it, click here.
 If you simply need to tighten your old chain, click here.
7. **Using a flat file or other straight-edge, check if the bar has uneven "high spots" along the edges that you can file down.** There is no top or bottom to most chainsaw bars, but one side will often start to wear out and chip. If this is the case, put the bar in a vice and careful file down any jagged, high edges so that the side is even again.

If the edges of the guide bar have become flared from heavy use, they may interfere with the smooth cutting of the chain, making it difficult to cut straight, if at all. If the edges or the grooves become worn, it may be time for a replacement guide bar.
While the chain is off the saw, check the saw's drive sprocket for excessive wear. It is not  unusual to need a new drive sprocket after wearing out multiple chains.
8. **Figure out which way the chain needs to face so the blades pull forward.** The chain pulls forward, meaning the chain on top of the bar moves away from your body. The saw blades (or "cutters") will point obviously in one direction, with the teeth all pointing the same way. The teeth on the top of the bar should point forward.
9. **Lock the chain into the grooves on the bar.** Put the blade on the bar so that the saw teeth on top of the blade push away from you. Make sure that they fit snugly.
10. **Remove the cover over the blade area and attach the bar.** Pull the chain around and lock it into the sprocket that powers the chainsaw (a large, round, spin-able part with grooves to lock into the chain). Then attach the bar snugly to the motor of the chainsaw according to your specific manufacturer's instructions.
With some types of sprockets, you may need to insert the bar without the chain on it, then loop the chain around the drive sprocket, finishing up by aligning the chain loosely into the groove on the guide bar.
11. **Reattach the covering so that the bar is snugly and firmly in place.** You want the bar on and chainsaw re-assembled before making your tension adjustments.
Do not completely tighten the attachment nuts yet because they serve to clamp the bar into position, and it needs to be adjusted first.
12. **Hold the nose of the bar up slightly as you work.** Throughout the next few steps, use your free hand to slightly lift the nose of the bar up, bringing it snugly against the attachment mechanism. The rest of the chainsaw should rest on a clean, flat surface.
13. **Find your adjusting screw or knob and tighten it until the blade is snug on the bar.** This screw is often found perpendicular to the direction of the chain. It will move a small pin that catches the bar, making it slightly shorter or longer to add or subtract tension. Check your owner's manual if unable to locate the screw, though it should be easy.
Sometimes the adjustment screw is located between the mounting studs. It could also be on the outside of the chainsaw, on the bar cover or on the engine.
14. **With hands still gloved, and the safety brake off (if applicable to your saw) manually pull the chain loop around the bar to check for tight spots.** If the blade doesn't move smoothly all the way around, lightly loosen the adjustment screw so that it can slide with ease. You want the blade on snugly, covering the whole bar, but not so snug that it can't move and cut easily.
A "perfect" middle ground to shoot for is 1.25mm of space between the chain and the bar, on the bottom half.
15. **Hold up the tip of the bar again and tighten the nuts or screws or knob that hold the cover on the saw, clamping the guide bar firmly into place, with the chain at the proper tension.** Do a final check that the chain still moves freely around the guide bar.
16. **Re-install the spark-plug wire, so you're ready to start the saw next time.** 
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