You’ve decided it’s time to trim those tree limbs hanging over your deck or, perhaps, you’re going to cut up some firewood from a fallen tree to add to the stockpile. You take the chainsaw out of the tool shed, fire the engine up, pull the throttle trigger… and are disappointed to discover the chain is not rotating cleanly. You remember installing a new chain only last fall and the chainsaw was cutting fine at the time. You hold the chainsaw up to get a better look and then you see it: the chain bar is bent!
Why the chain bar is vital for proper chainsaw operation
A damaged chain bar is one of the top causes of a chainsaw failing to cut properly. So, what does this part do exactly? The chain bar is usually aligned on mounting bolts attached to the main engine housing to support the cutting chain which rides in a track on the bar. The chain bar is designed to slide back and forth on the mounting bolts in order to adjust the chain tension. A tensioner pin attached to the clutch cover inserts into a small hole in the chain bar. By rotating a tensioner screw or knob, the pin will shift the chain bar back to loosen the chain tension or forward to tighten the chain.
Keep the chainsaw chain tension properly adjusted
It’s important that the cutting chain tension is adjusted correctly. If the chain is too loose, it may not be able to make good contact with the wood, or the chainsaw’s drive gear may not engage properly. A loose chain could also become dislodged from the chain bar and cause injury. If the chain is too tight, it will not rotate freely, reducing its cutting potential. In addition, a “too tight” chain can also damage the chainsaw’s engine or clutch. You should always follow the manufacturer’s guidance for the proper tension setting to get the optimum results from your chainsaw.
The chain bar uses oil to keep the chain rotating smoothly
When the chainsaw’s throttle trigger is pressed, the engine accelerates, causing flyweights attached to the clutch to extend outward. The clutch flyweights engage the drive gear which rotates the cutting chain. The clutch has another function as well: the spinning clutch operates a pump to supply oil to the chain bar. This specially-formulated chain oil is thick and designed to stick to the bar and chain to ensure the chain has enough lubrication to rotate smoothly. We recommend filling the chain oil reservoir every time you fill the fuel tank, but only use dedicated chainsaw chain oil; standard engine oil is not a suitable substitute. You should also keep the oiler hole (where the chain oil excretes from) clear of debris to ensure proper lubrication; otherwise, the chain bar, cutting chain, or engine could become damaged.
How does a chainsaw’s chain bar become damaged?
There’s always the potential for the chain bar to become bent, or damaged in some other way, after repeated use or if the equipment is stored improperly (such as having other objects stacked on top of the chainsaw). Fortunately, a bent chain bar doesn’t mean you’ll need to buy a new chainsaw; you’ll just need to replace the old, damaged bar with a new one… and this is something you can do yourself.
14 easy steps for replacing a chainsaw chain bar
While the exact procedure to replace a chainsaw chain bar will vary from model to model, Repair Clinic has 14 general steps you can follow to complete the repair successfully:
- Before you begin any disassembly, make sure the chainsaw engine has cooled, the on-off switch is in the “off” position, and the chain brake, if applicable, has been disengaged.
- Your next step is to remove the clutch cover. Be aware, you may need to detach an upper engine housing cover before you can fully remove the clutch cover. The clutch cover may be secured with nuts that will need to be unthreaded or you may need to push and rotate the chain bar tensioner knob to release the cover.
- Depending on the chainsaw model, you may now need to lift off a retaining plate holding the chain bar in place.
- Next, push the chain bar back towards the engine to loosen the cutting chain and you can remove the old chain bar and chain.
- Remove the new chain bar from its packaging.
- If your chainsaw has a chain guard, transfer the guard from the old chain bar to the new one.
- Align the cutting chain on the new chain bar. To do this properly, the teeth of the chain should face towards the front end of the chain bar on the top and away from the front end on the bottom of the bar.
- Loop the chain onto the clutch sprockets as you align the chain bar on the mounting bolts.
- If applicable, replace the chain bar retaining plate.
- Realign the clutch cover by inserting the tensioner pin into the hole in the chain bar – you will probably need to adjust the position of the pin to fully seat the cover.
- As applicable to your chainsaw, hand-tighten the mounting nuts or rotate the chain bar tensioner knob clockwise to loosely secure the clutch cover.
- Lift the chain bar up and rotate the chain adjustment screw or dial clockwise until there is no slack in the chain. As noted above, you should follow the manufacturer’s guidelines for the proper tension setting.
- With the chain tension properly set, tighten the mounting nuts, or rotate the tension knob to fully secure the clutch cover. If applicable to your model, reposition and secure the upper engine housing cover.
- Return the on-off switch to the “on” position and your chainsaw should be ready for use.
Troubleshoot and fix other common chainsaw problems
Is your chainsaw running rough? Does it start then stall, or maybe, not start at all? Repair Clinic has some very practical troubleshooting tips to assist you in figuring out why your chainsaw is malfunctioning. You can also find a wealth of model-specific procedural videos, step-by-step guides, diagrams, and schematics in the website’s “Videos & Articles” section to take the guesswork out of replacing the chainsaw’s clutch assembly, carburetor, fuel filter, or throttle trigger.
Only use genuine OEM replacement parts for your chainsaw
If you need to replace your chainsaw’s chain bar, you not only need to locate the right chain bar that fits your equipment but, as with any repair, you should only install a genuine replacement part from the original chainsaw manufacturer. Meaning if you have a Stihl chainsaw, you will want to make sure you are using Stihl chainsaw parts. Repair Clinic can help you do both. Enter the chainsaw’s full model number in Repair Clinic’s “Search Parts Online & Get Answers” search bar to view a complete list of compatible OEM parts direct from such manufacturers as Craftsman, Echo, Homelite, Husqvarna, MTD, Poulan Pro, Ryobi, Stihl, and Tanaka. You can then use the “Part Category” filter (“Chain & Bar”) followed by the “Part Title” filter (“Chain Bar”) to find the exact chain bar for your model. Providing you with the right part and the guidance to fix outdoor power equipment, home appliances, and heating and cooling units yourself is what makes Repair Clinic your repair partner for this season and the next.