Pole Saw: Chain Falls Off

The chain rotates inside the channel of the bar on the bar rail. Over time, the chain will stretch and the drive teeth on the chain will wear down, causing the chain to fall off the bar. When this occurs, replace the chain. Remove the cover and pull the chain and bar off. Remove the old chain and clean out the bar with a small screwdriver. Lubricate the bar with a bit of bar oil, then install a new chain around it with the chain around the drive sprocket. Install, cover, and tighten the nut tightly. You might have to back off the tension screw for proper alignment in the chain bar, then adjust tension on the chain by rotating the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Tighten down the cover and double check the tension on the chain, as it may have changed after the final tightening of the cover.

The bar supports the chain during rotation. The bar should be cleaned regularly and checked periodically for signs of wear. First, check the bar by wiggling the chain back and forth inside the rail. If you can wiggle the chain, the bar should be replaced. If the nose wheel bearing has too much play, the bar needs to be replaced. Check for wear behind the nose wheel. If it is worn on one side, flip the bar around and that will buy you some time. If it is worn on both sides, it’s time for a new bar. To install a new bar, remove the cover and pull the bar and chain off. Next, remove the chain from the bar and discard the old bar. Lubricate the new bar with a little oil, install the chain onto the bar, then back onto the pole saw, making sure the chain is around the drive sprocket. Install the cover with the nut hand tight. You may have to back off the tensioner so it is properly aligned into the hole in the chain bar. Adjust tension on the chain by rotating the adjuster screw clockwise. You should tighten the chain enough so that you can rotate it with one hand without the drive links coming out of the bar nose. Tighten down the cover and double check the tension on the chain, as it may have changed after the tightening of the cover.

The drive sprocket drives the chain around the bar. If the drive sprocket is worn, it can impact the tension on the chain, causing the chain to slip off. Remove the nut on the cover and pull the cover off. With the cover off, inspect the drive sprocket for signs of wear such as worn-down teeth, damaged teeth, chips, grooves, or anything else that looks like it will impact operation of the drive sprocket. To replace the sprocket, remove the E-clip holding it in place and remove the sprocket from the pole saw. Install a new drive sprocket and reinstall the E-clip. Re-install the cover with the nut, hand tightened. You may have to back off the tensioner to get it properly aligned into the hole in the chain bar. Then adjust tension on the chain by rotating the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Tighten down the cover and recheck the chain tension as it may have loosened after tightening the cover.

The adjuster allows you to set the proper tension on the chain. If the adjuster screw has become stripped or damaged, it will impact the performance of the adjuster. Remove the cover and tensioner screw from the cover by rotating it with a screwdriver. Remove the screw, tensioner, and retaining clip. Next, install the new retaining clip into the slot in the cover. Install the screw through the retaining clip and tensioner. Continue to thread until the retaining clip snaps over the hub on the screw. Next, rotate the screw counter clockwise to shift the tensioner towards the bottom half of the screw. Reinstall the cover. See pointers for re-installation under the “Bars” header, elsewhere on this page.

The retaining ring holds the adjustment screw in place, and keeps the tension on the chain. If this ring breaks or becomes damaged, it will no longer hold the screw and the tensioner in place. To check and replace, remove the cover. Locate the retaining ring. If it is broken, remove the screw and tensioner. Install the new retaining ring into the retaining slip, then thread the screw through the retaining ring and tensioner. Continue to thread until the retaining clip snaps over the hub on the screw. Next, rotate the screw counter clockwise to shift the tensioner towards the bottom half of the screw. See re-installation instructions for putting your pruner back together under the “Bar” section elsewhere on this page.