Pruner: Engine Rotates But Chain Doesn't

Make sure you are installing the correct adapters/extensions for your model and make sure they are installed correctly. Follow the owner’s manual for instructions on the correct adapters and extensions for your pruner, and guides for installation.

The gears transmit the power inside the pruner head from the drive shaft to the drive sprocket. If these gears become stripped or damage, they will cause the chain not to rotate. To check these gears, remove the 2 drive shafts from each other as it may make the pruner easier to work on. Remove the nut on the cover then pull the cover off altogether. Remove the chain and the bar. Remove the oil tank and use a flat-head screwdriver to help remove the oil tube from the tank. Remove the center screw on the shaft and loosen the rest of the screws on the pruner head housing, securing the two halves together. Remove the E-clip holding the drive sprocket and remove the sprocket and washer. Remove the screws holding the two halves together and separate the housing. Now you can inspect the gears. Trying rotating the gears by hand to see how they operate, and take a picture with your phone to remember their location. Check for visible signs of damage that might impact operation. Replace the bad gears, making note of where they come out. Lubricate the gears with grease and reassemble the pruner head by rejoining the two halves together (do not fully tighten the two screws where the shaft goes in). Re-install the washer sprocket and E-clip. Insert the lower drive shaft into the pruner head and make sure the shaft holes are aligned. Re-install the center screw and tighten the two screws by the shaft. Re-install the oil tube into the tank, then re-install the tank. Install the chain and bar with the chain around the sprocket. Install the cover and tighten by hand. See our advice on completing the repair and putting your pruner back together good as new under the “Bar” section, elsewhere on this page.

The shafts transmit power from the engine to the pruner head. If a shaft is binding or broken, it will not turn. To fix the shafts, start by loosening the locking nuts and handle that secure the upper and lower drive shafts together. Then, loosen the screws on the pruner head or engine housing on the shaft that isn’t working, remove the center screw and the old shaft, and replace it with a new one. Re-insert the new shaft into the engine end or pruner head by aligning it with the aligning hole then tightening the screws down. Re-insert the aligning screw and tighten down, then re-attach the two drive shafts back together and tighten down the locking nut and handle.

The bar houses the rail that the chain runs on for cutting. If the bar becomes badly clogged up with debris, it can stop the chain from rotating. Remove the pruner head cover and pull the bar and chain off, then remove the chain from the bar. Inspect the inside of the chain for debris and clean out if necessary. Once clean, inspect the inside for signs of damage. Check that the bar is perfectly straight and not bent. If it is bent or crooked then it needs to be replaced. Apply a little bar oil to the cleaned bar or the new one, then re-install the chain around bar and sprocket on the pruner head. Tighten the nut on the cover by hand. Note: you might need to rotate the tensioner counter clockwise to properly align it into the hole in the chain bar. Adjust the tension on the chain by rotating the screw clockwise. (Chain should be sufficiently tight so it can be turned with one hand, and the drive teeth must remain in the nose of the bar.) Tighten down the cover and recheck the tension, as it may have changed during the final tightening.

The drive sprocket rotates the chain in the pruner head. If the sprocket becomes badly worn, the drive teeth on the chain can skip over the sprocket, causing the chain to not rotate. Remove the nut on the cover and pull the cover off. Remove the bar and chain and inspect the sprocket. If it is badly worn, it will be noticeable via things such as chipped or broken teeth and grooves. To replace the sprocket, remove the E-clip holding it in place. Remove the old sprocket and install a new one. Re-install the E-clip then the bar and chain, ensuring the chain is around the drive sprocket. Install and hand-tighten the cover – you may have to rotate the tension screw counter clockwise to align the tensioner into the hole in the chain bar. Next, adjust the tension by rotating the screw clockwise. (The chain must not come out of the nose of the bar and should be easy to turn with one hand.) Tighten the cover and re-check the tension on the chain, as it may change throughout the process of tightening the nut on the cover.

The clutch transmits the power from the engine to the drive shaft by centrifugal force. As the engine speeds up, the clutch rotates faster, locking into position and transmitting the power. When the clutch is burned out, it will usually have a burning smell and start to slip. At this point, it needs to be replaced. Start by removing the spark plug wire and the spark plug to prevent an accidental start up. Remove the screws attaching the handle to the engine housing, then separate the two halves of the handle. Remove the spring on the throttle control, making note of how the spring is installed for when you have to reassemble. Remove the throttle cable from the control and disconnect the switch wire connector. Next, loosen the screws that hold the upper drive shaft in place, and remove the center screw, then remove the drive shaft. Remove the screws on the top cover and remove the cover altogether. Remove the clutch cover and rotate the flywheel to get the piston to bottom dead center – stick a small screwdriver down the spark plug hole to feel for the piston at the bottom. Next, insert a rope or cord through the spark plug hole to make sure the piston stays in the “down” position. Next use a clutch removal tool to remove the old clutch. Install the new clutch and use the clutch removal tool to tighten. Remove the cord or rope from the cylinder, re-install the clutch cover, then re-install the top cover. Re-install the upper drive shaft and use the locking screw to align the holes. Tighten the outside screws to secure the drive shaft, then remove the locking screw. Re-attach the switch wire connector and re-insert the throttle cable into the slot on the throttle control, then re-install the spring on the throttle control and re-install on the mounting pin inside the handle. Make sure you properly seat the spring on the pin. Next, re-insert the throttle cable and switch wire into the grooves inside the handle and re-assemble the two halves of the handle, then re-attach the handle to the engine housing and re-install the center screw. Re-install the spark plug wire and plug the wire back in.