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Home Do-It: Mower vibration may be blade issue

Sun., March 16, 2014, midnight

Q. I just got out my walk-behind, self-propelled lawnmower for the coming season. It started OK, but it seems to vibrate when running. I now remember that I hit a tree root last year and wonder if that has something to do with the vibration. What next – a repair shop?

A. You probably bent the blade a little and might only need a new blade, which you can install yourself.

If you have a manual for the mower, it should have instructions for changing the blade. Otherwise, pull the cable off the spark plug and tape the end so there is no chance of an accidental start-up. Drain the gasoline tank and pull the oil fill cap, then turn the mower on its side so the oil drains out into a pan. You can give the mower an oil change while you are checking the blade.

Mark the bottom of the blade with chalk to make sure it is re-installed in the correct position. A bent or damaged blade is often obvious, but sometimes the damage is so slight that the blade needs to be removed for close examination.

Some manuals recommend using a block of wood to hold the blade while the retaining bolt is removed, but I prefer to use a C-clamp placed on the housing so the blade bears against it. Wear gloves, and use a socket wrench if possible to remove the bolt.

Once the blade is free, lay it on a flat surface to see if has any obvious bends. If bent, it is best to replace it. Write down the model number of the mower and take it with you when shopping for a new blade. If the blade looks flat but the cutting edges are banged up and dull, use a file or grinder to sharpen them, or take the blade to a repair shop.

If you sharpen the blade yourself, the final step is to balance it. Set a thin, narrow piece of wood on edge on a flat surface and place the center of the blade over it. If the blade is heavier on one side, it will tilt. Balance can usually be restored by filing or grinding a little metal from the heavy side.

A properly tuned blade should not cause the mower to vibrate. If there is still vibration, it could be an engine problem requiring a small-engine expert to diagnose.

Q. Our main bathroom door sticks so badly our young daughter has trouble opening it. How can I correct this? I hope I don’t have to remove wood from the door – I don’t have many tools or the skill to use them. The sticking is at the top of the lock edge.

A. Door sticking is usually caused by misalignment of the door in its frame, and it can often be corrected without removing wood from the door. Start by checking all the hinge screws to make sure they are tight and holding the hinges snugly to the jamb.

Many times, loose screws in the top hinge will cause the door to sag enough to stick. Putting at least one 3-inch screw in each hinge attached to the jamb will usually strengthen the grip.

If all the screws are tight, you might be able to get the door working properly by shimming one or more hinges. Hinge shims are simply thin material, often thin cardboard. You can also buy plastic shims that are more durable and somewhat easier to install.

In order for shims to work, the door must have a slight gap between the lock edge and the jamb. Shims should be used behind the hinge leafs that attach to the jamb. If the door sticks at the top, try a shim or two on the top hinge. A door that scrapes the floor can often be unstuck by shimming the bottom hinge, tilting the door upward slightly.


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