Concrete Saw: Vibrates Excessively

A bearing is a device that is used to enable rotational movement of a shaft, which is supported by a stationary housing, reducing friction and handling stress. Because of the constant stress that bearings receive, they tend to wear out. Indicators of a worn bearing can give off a growling, humming, rumbling or screeching sound. Any of these symptoms, replace the bearing.
First, remove both belt covers. Depending on your model, one of the belt covers may be the recoil. Relax the tension on the belt by turning the tension nut counter clockwise until it stops. Take out the water line.
Next, remove the belt by walking it off both pulleys. Separate the blade assembly from the engine. Take out the but holding the pulley in place. For this step, an impact wrench works best. However, if you don’t have one handy, you can hold the pulley in place with channel locks to remove the nut.
Next, remove the arbor on the other side by inserting a screwdriver in the backside. This allows you to hold the blade steady as it comes arbor comes out. Pull off the arbor, blade, flanges and spacers off. Remove the blade cover. Clear any snap rings, bolts or screws necessary to detach the cutting device assembly. This will be different on all models. You can either replace this whole unit, which houses the bearings, or push the bearings out carefully. Do not damage the housing. Install new ones evenly into the housing then reassemble the unit back together.
Reinstall the blade cover, inner flange, spacer, blade, outer flange/spacer and lastly, the arbor and tighten. Reattach the pulley tight and add the belt back on by walking it on the pulleys. Apply the tension by turning the tension nut clockwise until it stops. Reinstall the belt covers/recoil.

The belt transfers power from the engine to the blade. If the belt is worn on part of its side, or is starting to fray, it can cause an excessive vibration. Remove both covers on the side of the concrete saw and inspect the belt. You may have to remove the belt for a better look. Turn the tension nut counter clockwise until it stops, and then walk the belt off both pulleys by pulling it over the pulleys and turning them by hand. Check that the sides of the belt are wearing evenly. If the belt has uneven wear, fraying or is cracking, it needs to be replaced. Install the new belt by inserting in on the pulley and walking it around the pulley by turning it. You will have to do this on both pulleys. Next, reapply the tension on the belt by turning the adjusting nut clockwise until it stops. Reinstall the belt covers.

If the blade is slightly warped, it will not spin true. This will cause a vibration and depending on how bad the blade is not true, the worse the vibration will be. Remove the blade by inserting a screwdriver in the access port on the one side of the blade and rotate the blade by hand until it locks in place. On the other side, use a wrench, or socket, to remove the nut. Take off both the flange and the blade. Lay the blade on a flat surface to check for flatness. Push down on it all of the way, moving around the surface. If the blade moves at all, then it is warped and you will need to replace it. Install the new blade followed by the flange and secure it by holding it in place with a screwdriver, tightening it with a wrench.

The flange helps support the blade. If a flange is warped, it will have some play in it and will lead to a vibration. This is because it cannot make full contact with the blade. Remove the arbor by inserting a screwdriver in the access port on one side of the blade and by using a wrench, take out the arbor on the opposite side. Remove the blade and both flanges. Lay the flange/flanges on a flat surface and inspect for flatness. To do this, push all the way down and move around to look for good movement. If there is any movement as you’re pushing down, the flange is bad and must be replaced. Install the new flange/flanges and the blade. Tighten down the nut by holding it in place with a screwdriver inserted in the back and a wrench on the nut.

The shaft, or axel, is what the blade rides on. If the axel is not straight, it will cause a vibration. Remove the arbor by inserting a screwdriver in the backside to hold the blade steady as you loosen the arbor with a wrench. Take off the blade, flanges, spacers and the shaft. Place the shaft on a flat surface and roll it along the flat surface, while inspecting it for a wobble. If you see any slight signs of a wobble, replace it. Reinstall the shaft back on the saw, along with the outer and inner flanges, the spacer and then put the arbor back on and tighten. Use a small screwdriver in the port on the opposite side of the arbor to hold the blade steady as you tighten.

Isolators are located inside the handle and act as a shock absorber, absorbing the vibration from the saw that travels in your hand and arm. Over time, and with use, the isolators can wear and break down. Locate the isolators in the handle and remove the screws holding the handle in place. Take out the isolators. Next, inspect the isolators by looking for rubber breaking down, cracks or chunks that may have broken off. Replace any bad isolators between the handle and the saw and reattach the handle back on the saw.