How to fix a chainsaw chain that won’t stay tight

Is there anything more annoying than a chainsaw chain that just won’t stay tight? Not only does a loose chain mess up your cutting, but it can also be downright dangerous. If you want to keep your chainsaw running smoothly (and safely), it’s good to know why the chain keeps loosening and how you can fix it yourself.

The tips in this article might not fit every chainsaw out there. We try to dish out helpful advice for DIY repairs, but different models can differ when it comes to troubleshooting, parts, and so on. For the best info, check your chainsaw’s manual or reach out to us if you’ve got questions.

Why your chain won’t stay tight

Chainsaw chains can loosen up for all sorts of reasons. Maybe you didn’t install or tension it quite right, or maybe some parts are worn out. Here are some usual suspects:

• Chain tensioner issues: The tensioner’s job is to keep the chain snug. If it’s messed up, dirty, or put in wrong, the chain might loosen up on you.
• Worn-out guide bar: The bar that holds the chain can wear down over time, which affects how tight the chain sits.
• Bad chain installation: If the chain isn’t fitted right around the bar and sprocket, it can slip.
• Chain’s worn or stretched: Chains naturally stretch as you use them, so an old chain might come loose more often.

Safety precautions   

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind: 

• If working indoors, make sure there is adequate ventilation to prevent the buildup of exhaust fumes. Carbon monoxide poisoning can be a serious risk.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Never attempt to service or repair while it is running or when the engine is still warm. Wait for all moving parts to come to a complete stop.
• Exercise extreme caution when working near blades, augers, or any other moving parts. Keep your hands, fingers, and clothing clear of these areas at all times.
• If the appliance has recently been used, give it plenty of time for any hot parts to cool down before working on it. 
• Empty the gas tank before beginning any work. Refill using fresh fuel. 
• Clean up oil spills right away to prevent slipping or other damage. 
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• When not in use, store the machine in a safe and dry location.

Confirm proper chain installation

Even a shiny new chain can come loose if it’s not put on right. Chains have sharp cutting teeth on one side and drive links on the other. Those drive links need to sit snugly in the bar groove and fit the saw’s drive sprocket. If they’re not properly seated, the chain can slip off.

Step-by-step instructions

1. Pick the right chain: Chains vary in pitch, gauge, and link count. Make sure you’ve got the correct chain for your bar and sprocket. Check the packaging or your manual to be sure it matches up.
2. Power down: Always make sure the chainsaw is off. For gas models, pull off the spark plug wire. For electric ones, unplug it or remove the battery.
3. Loosen the bar nuts: Take off the side cover and turn the tensioner screw counterclockwise so the bar can move freely.
4. Position the chain around the sprocket: Align the chain’s drive links with the sprocket teeth. Make sure the cutting edges face the right direction (usually forward on the top side of the bar).
5. Seat the chain on the bar: Guide the drive links into the bar groove, making sure they slide in smoothly.
6. Adjust the tension: Turn the tensioner screw clockwise until the chain is snug. Lift the chain slightly from the bar—it should move just a bit before snapping back into place.
7. Tighten the bar nuts: While holding the bar nose up, tighten the bar nuts firmly. If you let the bar droop before tightening, the chain might loosen when you use it.
8. Double-check: Rotate the chain by hand (don’t forget gloves). If it spins freely without sagging, you’re good to go.

Fine-tune your chain tension

Sometimes, it’s not the chain or the bar that’s the problem—it’s how you adjust the tension. Using the right technique helps the chain stay tight longer. Here’s how to dial it in:

Important tensioning tips

1. Warm it up: Chains stretch a bit when they heat up. If you tighten the chain when it’s cold, it might loosen once you start cutting. Make a few cuts first, then turn off the saw and adjust the tension again.
2. Check the tension often: If you’re cutting for a while, check the chain tension whenever you refuel or add oil. It takes just a second and can keep the chain from getting too loose.
3. Keep the bar tip up: When tightening the bar nuts, be sure to lift the tip of the bar a bit. Letting it sag can introduce slack in the chain.

Check your chain tensioner

The chain tensioner’s job is to hold the chain steady. When you turn the adjustment screw, it moves the bar forward or back to tighten or loosen the chain. If you think the tensioner’s the problem, here’s what to do:

Step-by-step instructions

1. Disconnect power: Before any repair, make sure the chainsaw is completely off. If it’s electric, unplug it or take out the battery. If it’s gas-powered, pull off the spark plug wire so it can’t start accidentally.
2. Expose the tensioner: Find the side plate or cover that holds the chain and bar. Remove the nuts or screws to take off the cover.
3. Inspect the tensioner mechanism: Look for any cracks, bends, or broken parts. Also, check for sawdust or gunk that’s keeping the tensioner from sliding smoothly.
4. Clean the area: Use a brush or rag to get rid of debris. If there’s stubborn grime, a little chainsaw solvent can help.
5. Test the tensioner: Gently turn the tension adjustment screw. Watch if the tensioner peg (the little metal piece that fits into the bar’s hole) moves smoothly. If it’s jerky or doesn’t move, the screw or peg may be damaged.
6. Replace if necessary: If cleaning doesn’t fix it, you might need a new tensioner. Check your manual for the right part number so you get the right one.
7. Reassemble and test: Once the tensioner’s clean and working, put the cover back on and tighten the nuts. Test the chain tension again. If it stays tight now, you’ve solved the tensioner issue.

Inspect your guide bar

The guide bar keeps the chain aligned and helps control tension. Over time, it can get worn down, develop burrs, or even warp—all of which can make the chain come loose. A bent or worn bar won’t keep the chain tight.

Signs of a worn guide bar

• Visible grooves or ridges along the rails
• Uneven or shiny spots from friction
• The chain tilts to one side during operation

Step-by-step instructions

1. Remove the bar: Turn off the chainsaw and remove the side plate like you did before. Carefully slide out the guide bar once the chain is off.
2. Examine the bar rails: Look along the edges of the bar. If you see metal flaking or deep grooves, the bar might be too worn to use effectively.
3. Check for straightness: Lay the bar on a flat surface to see if it wobbles. A warped bar makes it tough to keep proper chain tension.
4. Remove burrs or minor wear: You can use a flat file to take off small burrs, but remember, too much filing can weaken the bar. If you’re not sure whether to file or replace, check the manufacturer’s guidelines.
5. Flip the bar: If the bar’s symmetrical, some manufacturers suggest flipping it over now and then to promote even wear. But if it looks beat up, it’s safer to replace it.
6. Reinstall the bar: Put the bar back on the saw, making sure it fits snug with the tensioner peg. Reattach the chain and put the side cover back on, but don’t tighten the nuts all the way just yet.
7. Set chain tension: Pull the chain forward to seat it on the bar. Adjust the tensioner screw so the chain fits snugly without binding. Tighten the cover nuts to lock everything in place.
8. Test run: Give it a quick test. If the chain still loosens, it might be time for a new bar.

Where to go from here

Thanks for reading! If you need replacement parts, grab your model number and head to AppliancePartsPros.com. We offer over two million parts and most orders arrive in two business days. If you need help finding the right part or placing an order, you can contact our team at 1 (877) 477-7278.

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