Hedge Trimmer: Vibrates Excessively

The purpose of a bearing is to allow a moving part to move inside of a stationary part. Bearings can wear out and cause a vibration between the moving and stationary part. To determine if the bearings in your hedge trimmer are causing it to vibrate excessively, you will need to inspect it manually. To do this, remove all the locking nuts securing the blades and remove the blade guard tip guard with their associated washers. Next, remove the gear case cover and remove all the blade mounting bolts with washers. You can now remove the felt seal and the lower gear. Be careful as you remove the lower blade, spacer plate, upper blade, and upper gear. At this point, wiggle the drive gear to check for excess movement. If you find that there is play when you wiggle it, remove the screw holding the gear case to the engine block and remove the retaining ring using snap ring pliers. Now you can pull the clutch drum out, and use internal snap ring pliers to remove the bearing retaining ring. Using a flywheel puller, you can now remove the bearings. Replace both bearings by aligning them and use the fly wheel puller to fully seat the bearings. Secure the bearings with the retaining rings, and reinsert the clutch drum into the gear case, securing it with the ring. Now you can re-attach the gear case to the engine block and position the inner gear so the holes are in line with the blade support (note: you should add a little white grease between all these moving parts during re-assembly). At this point, align the top blade with the sharp edge facing away from the blade support. Re-install the spacer plate and install the lower blade with the sharp edge facing away from blade guide. Replace the lower gear with the cam aligned on the opposite side of the inner gear cam. Make sure the holes in the gear are in proper alignment with the blades. Next, you can adjust the lower blade until the gear sets into place. Re-install the felt seal, new gasket, and cover. Re-attach the trimmer blades back into the blade support. Re-align the blade guards onto the mounting bolts. You will need to use new locking nuts to secure the bolts as they are designed for one-time use.

If blades are bent or damaged, they can cause an excessive vibration. To fix this symptom, the blades will either need to be bent back into shape, or replaced with new ones. One common blade issue that typically results in this issue are bent blade teeth. This will cause vibration as they oscillate. You can easily fix this problem by loosening the bolts on the blade guide and bending the teeth with pliers. If you require blade replacement, then remove all the locking nuts securing the blades. Next, remove the blade guard and tip guard with the washers. Then, remove the gear case cover and all the blade mounting bolts with washers. You can now remove the felt seal and remove the lower gear. Carefully remove the lower blade, spacer plate, then the top blade. Now you’re ready to install your new blades. To do this, position the inner gear so the holes are in line with blade support. You will want to add a little white grease in between all these moving parts during reassembly. Align the top blade with the sharp edge facing away from the blade support, and re-install the spacer plate. Install the lower blade with the sharp edge facing away from blade guide. Re-install the lower gear with the cam aligned on the opposite side of the inner gear cam. Make sure the holes in the gear are in proper alignment with the blades. Adjust the lower blade until the gear sets into place. Now you can re-install the felt seal, new gasket, and cover. Re-install the trimmer blades back into the blade support. Then realign the blade guards on to the mounting bolts. Use new locking nuts to secure the bolts as locking nuts are designed for one time use.

Loose bolts that keep your trimmer’s handles in place can cause it to vibrate excessively. Check if any of the bolts are loose, and tighten as necessary. This should solve the problem simply and effectively.

The purpose of the housing is to house the engine and all the parts. Loose hardware on the housing will cause excessive vibration. To determine if the housing is causing this symptom, go over the entire unit checking all the mounting bolts. Any broken or missing ones will need to be replaced with the manufacturer’s recommended bolts.

The cover’s job is to protect the engine. If it is vibrating on its own, tighten the hold-down bolts. The cover will not cause excessive vibrations on its own. If tightening the bolts on the cover does not fix this symptom, then the cover is not the cause.

The crankshaft bearing in your hedge trimmer can be found between the bearing and crank case. These bearings are extremely durable and will usually only require replacement after a severe lack of maintenance. Replacing the crankshaft bearings is a somewhat difficult repair. However, if you decide to take on the repair, you will want to begin by draining all fuel from the tank, and removing the air filter and the air filter bracket. Next remove the throttle cable and fuel lines from the carburetor and remove the carburetor itself. Now you can remove the isolator block gasket and isolator block. Remove the spark plug wire and the plug itself, then remove the motor housing. Remove the insulator gasket, the starter, fuel tank, and air duct. Now you can separate the clutch shaft screw that secures it to the engine. Slightly tap the motor off with a rubber mallet. Next, insert the starter rope into the cylinder through the spark plug hole to stop the piston from moving. Using a pair of channel locks, you can now remove the clutch. Disconnect the flywheel by pulling on it as you tap the center spindle with a rubber mallet. Next remove the starter pulley, muffler, and cylinder. Separate the cylinder from the crankcase and separate the 2 halves of the crank case from one another. To separate the crank case halves, you will need to push the crankshaft through the bearing. To do this, you can use a rubber mallet to tap the shaft. Now remove the crank shaft on the other side with the rubber mallet. You will have to remove the crankshaft bearing seals on both ends of the crankcase. To accomplish this, place the crankcase seal-side-down and insert a screwdriver through the center of the seal and tap it out with a rubber mallet on both sides. To remove the bearing, use a socket that fits on top of the bearing and tap it with a rubber mallet on both sides. Now you can install the new bearings and start reassembly. To do so, insert the new bearings and attach a socket big enough to make contact with the outer race of the bearing and tap with the mallet. Repeat for both sides and insert new bearing oil seals. You will want to rub a little oil on them first, then tap them into place using a socket. Install the larger side of the crankshaft into the case first (after lubricating with oil) and insert the longer end into the crankcase. You may have to tap it into place with a rubber mallet. Next, install a new gasket where the 2 crankshaft seals join and re-assemble. Insert screws to pull the housing back together and work all the way around to pull it down evenly. This will create a solid seal and not damage the gasket. Now you can re-install the cylinder onto the crank case and replace the gasket. First, make sure the old gasket has been cleaned off completely and be sure to lubricate the inside of the cylinder before you reinstall it. Make sure the ignition coil is on the same side the flywheel. Next, you can reinstall the starter pull and flywheel, making sure to align the flywheel with the markings. You can now reinstall the clutch and be sure to tighten it properly. Remove the starter rope from cylinder. Now you will have to reset the gap between the flywheel magnets and the ignition module. You can accomplish this by using an ignition coil gapping tool. You will want to slightly loosen both screws on the ignition coil and rotate the magnets on flywheel into the place of contact on ignition coil. Insert the gapping tool and allow the magnets to pull the coil tight against the flywheel. Then you can tighten the ignition coil and re-install the muffler and new muffler gasket. Re-install the engine assembly back onto clutch assembly and reconnect the ignition wires. Next, re-install the fuel tank, air duct, and starter. It may need to be rotated slightly to engage the pawls. Install the screws and tighten the back up. Install the insulator gasket and re-install the cover and tighten it properly. You can now re-install the sparkplug and wire, as well as the carburetor insulator and be sure to tighten the bolts. You can now reconnect all the fuel lines. Press the primer bulb to determine which port on your carburetor is the incoming line and which is the return line. Re-attach the fuel lines to the correct port, and reattach the throttle cable, being sure to tighten the cable nut down. You can now re-install the air filter bracket, the base, the carburetor, and the intake gasket, and tighten down properly. Finally, install the air filter and cover.