The Big Four

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Routine maintenance eliminates most mower trouble

By Greg Summers

It happens on Saturday mornings from April through late October.


A gung-ho, do-it-yourselfer steps outside, breathes deeply and heads to the shed to get out the mower.

He checks the fluids, adjusts the throttle and either pulls the crank cord or turns the ignition switch.

Nothing happens.

Then, he wastes half the day trying to get the mower started. And if it doesn’t, he loads up the mower to take it to a repair shop on Monday.

With more and more penny-pinching homeowners taking broken-down mowers to repair shops instead of buying new ones, that repair line is much longer.

“Mondays and Fridays are definitely our busiest days,” said Kevin Sowell of Small Engine Supply. “On Fridays, they’re getting ready to mow and on Mondays, they’re trying to find out what’s broken and why it won’t run.”

What’s broken could be eliminated with a little routine mower maintenance.

“They just don’t do it,” Sowell said. “There are more problems from people not doing maintenance than from part failure.”

Charles Clark of Home Specialties estimates that at least 50 percent of mower breakdowns are caused by the lack of routine maintenance.

This includes changing oil, changing the spark plug and installing new air and gas filters. When sharpening blades is added in, Clark calls it the “Big Four.”

“Routinely changing oil and air filters are big and, to be honest, a lot of people just don’t do it,” Clark said. “Any air-cooled motor is going to use a little oil and you have to keep up with things like that.”   

Home repair guru Danny Lipford, host of the nationally syndicated television show, “Today’s Homeowner,” has a mower maintenance video posted on his website, www.dannylipford.com.

Lipford said a properly maintained mower ensures that it will operate safely and last for years, giving you a good return on the investment.

“They are easy,” he said. “There are three or four things you can do to make it work better.”

A detailed schedule is included in the owner’s manual, but a lawn maintenance schedule should include changing the oil, spark plug, air filter and sharpening the blades. 

Change the oil

A lawn mower’s engine oil should be changed after the first five operating hours and then after every 50 hours of operation, or every season. In dusty or dirty conditions, oil changes may need to be more frequent. If operating under heavy loads or at high temperatures, the engine oil should be changed every 25 operating hours. Here’s how:

– Run the engine for a few minutes to warm the oil so it flows better.

– Stop the engine and wait for all the moving parts to stop.

– Disconnect the spark plug wire.

– Remove the drain plug and drain oil. Some mowers don’t have drain plugs and will need to be tipped over so the oil can drain out the dipstick/filling port. Be care not to spill any oil on the air filter.

– Install the drain plug or return the mower to an upright position. Fill the crankcase to the “Full” line on the dipstick. Use the oil recommended by the owner’s manual and just add a little at a time until full.

– Replace dipstick and use a rag to wipe up any spills.

“Just make sure to fill it up to the right level and dispose of the old oil properly,” Lipford said.

The spark plug

An old spark plug that’s dirty, pitted, covered in carbon or has a worn electrode can result in hard starts and poor operation.

A spark plug should be replaced after 50 operating hours. The type of spark plug you need will be in the owner’s manual or listed on a label on the lawn mower.  Here’s how:

– Stop the engine and wait for all the moving parts to stop.

– Disconnect the spark plug wire.

– Clean any debris around the spark plug housing.

– Remove the spark plug with the appropriate deep socket and clean it with a wire brush to remove any carbon buildup.

– Inspect the plug for cracks, damage or worn electrodes. Replace if necessary. Set the gap on the plug, if needed (check owner’s manual).

– Install spark plug by hand, then gently tighten with socket wrench. Do not overtighten and break the spark plug. Reconnect the spark plug.

“A spark plug is the brains of all of it,” Lipford said.

The air filter

– Cleaning the air filter not only improves mower performance, it also extends the life of the mower. Clean the foam pre-cleaner every 25 hours. Replace the paper air filter once a season or after 300 hours of operation. It may need to be changed more frequently with dusty conditions.    

“You’d be amazed at how dirty and dusty air filters get,” Lipford said. “It helps the mower breathe a lot better.”

Here’s how:

– Stop the engine and wait for all the moving parts to stop.

– Disconnect the spark plug wire.

– Remove air filter cover.

– Clean the foam precleaner with compressed air or rinse with water and cleaner and dry.

– Remove old paper filter and discard. Insert new filter, replace air filter cover and reconnect spark plug wire.

– Don’t operate mower without air filter or pre-cleaner.

– Don’t try to clean the paper filter. Replace it with a new one.

“It’s also a good idea to go ahead and change the gas filter, too, ” Sowell said. “Motors with carburetors don’t like the ethanol additives that are in unleaded gasoline. They can gum things up.”

Blade sharpening

Sharpening a blade can be done with a metal file, sharpening stone, a motorized grinder or drill motor chucked with an abrasive wheel.

Lipford said sharp blades make a big difference.

“If you don’t sharpen the blade, it’s just going to tear the grass up and won’t cut it cleanly,” Lipford said. “You’ll end up with a lot of diseases in your yard and it won’t look as good as it could.”

Here’s how:

– Drain the gas and disconnect the spark plug wire so the motor won’t turn over while you're working.

– Tilt the mower on its side, and wedge a block of wood between the blade and the mower deck to keep the blade from turning. You can also buy a device called a Blade Buster that locks the blade in place while you work on the mower.

– Use a scraper or putty knife to clean away built-up debris from the underside of the mower deck.

– Remove the bolt from the center of the blade.

– Pull off the blade and clamp it in a bench vise. Check the blade edges for small nicks and remove them using a flat medium file.

– Sharpen the blade by moving the file toward the cutting edge with smooth, even strokes. Follow the original bevel of the blade as closely as you can.

– Make the same number of strokes on each edge. If you take more metal off one side than the other, the blade will be out of balance. An out-of-balance blade cuts unevenly; it also makes the mower vibrate, which can seriously damage the engine.

– Test the balance by resting the blade on a dowel or the handle of a screwdriver. If one side points up, sharpen the other until the blade lies flat.