What Are the Common Causes of Chainsaw Chain Jumping Off the Bar?

What are the common causes of chainsaw chain jumping off the bar

As someone who frequently uses a chainsaw for yardwork and woodcutting, I know how frustrating it can be when the saw chain pops off the bar mid-cut. A loose or improperly tensioned chain can be dangerous and damage both the bar and chain. 

In this blog post, I’ll discuss some of the most common reasons chainsaw chains jump the bar and provide tips on proper maintenance and repair to keep your saw running safely and efficiently.

What are the common causes of chainsaw chain jumping off the bar?

What are the common causes of chainsaw chain jumping off the bar

There are several typical culprits behind chains jumping the bar, including worn-out components, improper chain tensioning, temperature fluctuations, using the wrong bar/chain combination, and cutting dense brush. Identifying the root cause is key to preventing further issues.

Worn-out chainsaw bar

One of the most common reasons a chain will derail is a worn out guide bar. The bar has a critical job – to provide a solid foundation and customized groove that matches the chain drive links. As the bar wears over time, the rails that guide the chain can become uneven or develop burrs and sharp edges. 

This damage disrupts the chain’s path and can cause it to pop out of the bar groove, especially on the tip where it’s moving the fastest. Checking for wear and replacing bars before they are badly damaged is key. Signs that the bar needs replacement include deep grooves, uneven rails, and excessive side-to-side chain movement in the groove.

Worn-out drive sprocket

The sprocket drives the chain around the bar and engages the drive links to pull the chain along. Like other moving parts, sprockets gradually wear out over time. The spur teeth that grab the chain will become rounded and smoothed, losing their ability to efficiently engage the chain. This can allow chain slack, slowing it down and increasing the chances it will jump the bar. Regularly inspect the sprocket for excessive wear and replace promptly when needed. Look for pointed, shark-fin shaped teeth – rounded stubs indicate replacement time.

Improper chain tension

Having the correct amount of tension is absolutely vital for safe chainsaw operation and preventing derailment. Chain stretches over time, slowly increasing slack. Temperature fluctuations also impact tension – chains contract when cold and expand when hot. Too loose and the chain will sag, allowing it to bounce out of the groove. 

Over-tightening restricts needed flex and increases friction and strain on the bar, chain, and engine. Set tension with the chain cold and check it frequently – the chain should have just a little up/down movement with light finger pressure. Refer to your saw’s manual for detailed tensioning procedures.


What Are the Common Causes of Chainsaw Chain Jumping Off the Bar?

Bar rails in poor condition

In addition to groove wear, damage to the guide rails that run along each side of the bar can also lead to problems. The rails help align the drive links with the bar groove to keep the chain tracking straight. Dents, burrs, and rust buildup on the rails obstruct free chain movement, increasing friction and chances of throwing the chain. Dress any burrs with a flat file and keep rails clean and lubricated. Replace bars with significant rail damage.

Temperature fluctuations

As mentioned previously, temperature has a direct impact on chain tension. Chainsaw chains are designed to run at a specific temperature. As they heat up during use, the metal expands and chain tension increases. Then when they cool down, tension drops again. Dramatic temperature swings between uses can cause the chain to loosen below the optimal level, allowing it to derail more easily. Monitor and adjust tension more frequently when operating in frigid weather or doing short, intermittent cuts.

Incorrect bar and/or chain for the saw

Chainsaws are designed for specific bar/chain combinations – the chain pitch and gauge must match the bar groove dimensions. Mixing and matching can allow the chain to rock back and forth excessively in the bar groove, soon leading to the chain catching and coming off. Refer to your saw manufacturer’s guide for proper bar and chain types. When replacing either component, be sure to match the pitch and gauge of the new piece to the old.

Cutting brush

While chainsaws are ideal for clean cuts through logs and firewood, attempting to cut dense brush with a saw is just asking for trouble. Groups of thin branches or saplings allow material to enter the chain groove from multiple sides. This packs into and clogs the groove, obstructing the chain’s path. The chain has nowhere to go but out. Save your saw chain and use loppers or a machete to clear brush instead.

Maintenance tips to prevent chainsaw chain issues

With proper care and maintenance, you can keep your chainsaw’s bar and chain in optimum working order for safety and efficiency. Here are some key areas to focus on:

Regularly check and adjust chain tension

Getting in the habit of checking tension every time you refuel is a good rule of thumb. The chain should have just a little bit of up/down play with light finger pressure. Refer to your saw’s manual and use the proper tensioning procedure – over-tightening can cause damage. When adjusting, always loosen the bar nuts before turning the tension screw.

Inspect and replace worn-out components

Routinely check the condition of the bar, chain, and sprocket. Look for wear, damage, and missing drive links. Replace parts before they become excessively worn to prevent malfunctions. Use manufacturer-recommended replacement components to maintain proper drivetrain alignments.

Properly lubricate the chain and bar

Proper oiling is what keeps the chain, bar, and sprocket from wearing out prematurely. Regularly check that oil is reaching the bar and chain – you should see some fling off the tip as the chain spins. Use only manufacturer-recommended bar and chain oil for optimal lubrication. Too little oil allows excessive friction, while vegetable-based oils can gum up in cold weather.

How to fix a chainsaw chain that has jumped off the bar

If a chain does come loose, don’t despair. With a little know-how it can be put back on and tensioned safely. Here are the steps:

Reinstalling the chain

First, examine the chain, bar, and sprocket for any damage that may have caused the derailment. Gently pull the chain back into the bar groove, starting at the tip. Often rotating the loose bit around the tip helps align it back into position. Pull it evenly around the rest of the bar by hand, being careful not to twist any links.

Adjusting chain tension

Before starting the saw, properly tension the chain – refer to your owner’s manual. Release the bar nuts, then turn the tension screw clockwise until the chain has just a little up/down movement in the middle. Hold the bar nose up and tighten down the nuts firmly.

Replacing worn-out components

If the chain derailment caused damage, you may need to replace sections of chain, the bar, or the sprocket before safely resuming use. Install manufacturer-recommended replacement parts that match the gauge and pitch of your saw.


I hope this overview gives you a better understanding of why chainsaw chains jump bars and how to help prevent issues through proper saw maintenance. While it can be startling when a chain pops off mid-cut, in most cases it’s an easy fix. Keeping your bar, chain, and sprocket in good working order will have you back sawing safely in no time. Let me know if you have any other chainsaw operation questions!

Frequently Asked Questions

How often should I check and adjust my chainsaw chain tension?

A good rule of thumb is to check tension every time you refuel your saw. Tension tends to gradually loosen over time, so frequent adjustments will prevent the chain from getting too loose.

How can I tell if my chainsaw bar is worn out?

Look for deep grooves, uneven rails, looseness/wiggle of the chain in the groove, and sharp burrs or hooks of raised metal. These all indicate replacement is needed. You can use a straight edge to check for uneven wear.

What is the proper way to lubricate a chainsaw chain and bar?

Always use manufacturer-recommended bar and chain oil. Check that oil is reaching the tip when running. Tension the chain properly to allow oil flow. For prolonged storage, dunk the bar tip in oil to prevent rust inside the groove.

Can I use any type of oil for lubricating my chainsaw chain and bar?

No, regular motor oils and vegetable oils can gum up, especially in cold weather. Use manufacturer-specified bar and chain oil, which is formulated to prevent fling-off and stick well across temperature extremes.

How do I know if my chainsaw chain is installed correctly?

The chain should move freely around the bar by hand and seat fully into the groove without any twisting of links. The drive links should align with the teeth on the sprocket. There should be a little up/down movement with correct tension.

What should I do if my chainsaw chain keeps coming off even after adjusting the tension?

If tension adjustments aren’t fixing the issue, examine the bar, chain, and sprocket closely. Look for damaged or worn out components like stretched chain, uneven bar groove, and rounded sprocket teeth. Replacing damaged parts can get the saw running properly again.

How can I prevent my chainsaw chain from jumping off the bar while cutting brush?

The best approach is to avoid using a chainsaw for cutting brush and saplings. The small branches easily pack into the chain groove, disrupting chain movement. Use loppers or a machete for clearing brush to protect your saw.

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