Pruner: Cuts Poorly or Not At All

The blades on the chain do all the cutting. Over time the blades can become dull with use and will need to be re-sharpened. Purchase a chainsaw sharpening tool with the same kerf as the chain. Start by taking the two drive shafts apart by loosening the locking nut and handle and separating them. Lock the bar in a vice in the center of the bar. Mark the first tooth so you know where you started. Sharpen each tooth facing you by running the sharpening tool at the exact same angle in the teeth upwards, 4 times on each tooth. Always utilize the full length of the sharpening tool and run it the same number of times on each blade for proper cutting. Rotate the chain to the next blade facing you. Once you have completed one side, remount the chain on the other side in the vice and perform the same sharpening on the other side.

The chain provides all the cutting teeth as well as all the drive teeth. If the chain starts to not cut as well as it used to, it could be due to a couple of reasons. The first possibility is that the cutting teeth are no longer sharp, and that will require you to re-sharpen them. The second possibility is that the drive teeth are worn that to the point that the chain will not rotate at full speed, or stops altogether under load. In this case, you will need to replace the chain. To do this, start by removing the locking nut and handle securing the lower and upper drive shafts together. Once removed, take off the nut on the pruner head cover and remove the cover completely. Remove the bar and chain. Install the new chain around the bar, then back onto the pruner head with the chain around the drive sprocket. Install the cover and tighten the nut by hand. You may have to back off the tensioner in order to properly align the tensioner into the hole on the bar. Adjust the adjuster screw to tighten the chain. Tighten the chain to the point you can spin it with one hand and to such a point as the drive teeth do not come out of the bar nose. Tighten the nut on the cover and re-check the tension on the chain, as it may have changed during final assembly. Re-install the two drive shafts together.

The shafts transmit power from the engine to the pruner head. These shafts have gears on the ends of them to allow them to connect to the engine, each other, and the head. If there is any damage or wear to these gears or the shafts then they must be replaced. For the lower drive shaft, start by removing the locking nut and handle on the lower drive shaft. Remove the cover on the pruner head, and then loosen the screws on the pruner head housing. Remove the center screw on the housing that holds the shaft in place. Remove the shaft and install the new one. Re-install the center screw tightly, and re-tighten the side screws. Slide the two drive shafts back together, lining up the alignment pin, then tighten down the locking nut and handle. For the upper drive shaft, remove the locking screw and handle on the lower drive shaft and separate the two shafts. Next, loosen the screws on the handle that secure it to the engine housing. Separate the two halves of the handle. To remove the throttle control, make note of where the spring is (take a picture with your cell phone for the most accurate way of making this note), then detach the spring and remove the cable. Disconnect the switch wire connector and loosen the screws securing the upper drive shaft to the engine, and pull the shaft out. Discard the old drive shaft and install the new one into the engine. Use the locking screw to align the screw holes, then tighten the screws down, securing the upper drive shaft to the engine. Next, remove the locking screw used to align the shaft then re-connect the switch wire. Re-install the throttle cable into the throttle slot located on the control and re-attach the spring into the control, and align the assembly onto the handle. Re-insert the switch wire and throttle cable into the grooves on the handle. Re-attach the two halves of the handle and screw tight, then align the locking screw and tighten down.

The bar provides the channel for the cutting blade to rotate on. If this bar becomes worn over time or the inside of the channel becomes damaged or gummed up with debris, it will need to be cleaned out or replaced. Start by taking the two drive shafts apart by loosening the locking nut and handle, then removing the cover, blade, and chain. Remove the chain from the bar and clean out all debris from the bar if it is badly gummed up. Inspect the channel for wear and damage. If you suspect any wear or see damage you will need to replace the bar, but if it is just full of debris and looks fine, you can re-use it. To install the bar, first install the chain over the bar then back onto the pruner head, making sure the chain is around the drive sprocket. Re-install the cover, hand-tightening the nut. You will likely have to ease off the tensioner in order to correctly line it up with the hole on the bar. Adjust the tension on the chain with the adjuster screw. (Ideally it should be tight enough to rotate with one hand without the drive teeth coming out of the bar nose). Finally, tighten down the nut on the cover and recheck tension on the chain, then install the drive shafts back together.

The drive sprocket drives the chain around the bar for cutting. If the drive sprocket is badly worn, it can impact the tension on the chain, causing the chain to cut poorly or even stop under a load. Loosen the locking nut and handle on the lower drive shaft to the upper drive shaft. Next, push the alignment clip in and pull apart. Remove the nut on the cover and pull the cover off the pruner head. With the cover off, inspect the drive sprocket for signs of wear such as worn-down teeth, damaged teeth, or grooves in the teeth. If the sprocket is showing any signs of wear, it must be replaced. To replace, first remove the E-clip holding the sprocket in place, remove the sprocket, and install a new one. Re-install the E-clip. See our instructions for putting your pruner back together after a repair of this nature under the “Bar” section on this page.