How to Tune Up a Grass Line Trimmer Video


This video shows how to tune up your grass line trimmer so it operates reliably and at peak efficiency. If you're having problems with your line trimmer, see our grass line trimmer repair help

How to tune up a grass line trimmer

It’s best to tune up your trimmer engine once a year. Following the service schedule in the owner's manual reduces the need for costly repairs later. The tune-up procedure we will show today is applicable for most trimmers.

For repair advice for appliance, garden equipment and more, check out all of Sears PartsDirect’s DIY repair help

Supplies You Might Need

Only two parts are needed to do the tune-up: a spark plug and an air filter cover. Besides the tools, you need a lubricant such as WD-40, shop rags or paper towels, a small amount of SAE 30 weight oil for the air filter, fresh gas and two-cycle fuel mix with fuel stabilizers. Nitrile gloves can be used if you have any concern about your skin coming in contact with fuel.

Before You Start

Be sure there are no open flames or ignition source in the area, because you're working with fuel. 

Drain the Fuel

If you store the trimmer over the winter with fuel in the tank, drain the tank. Stale fuel mix is one of the leading causes of trimmer failure. To drain the fuel, remove the fuel cap and poor the old fuel mix into an approved container. 

Once the fuel is drained, cap the container and set it aside so it doesn't accidentally spill.

Old fuel is considered hazardous household waste. Be sure to dispose of all fuel in accordance with applicable law. Most cities or counties have some type of hazardous waste recycling facility.

Replace the Spark Plug

After the fuel is drained, you can replace the spark plug. First, remove the spark plug wire and tuck it out of the way. Then remove the spark plug with the spark plug wrench.

Before installing the new spark plug, set the gap with the spark plug gapping tool.  Check the gap setting for your model in the owner’s manual. Once the spark plug is gapped, thread the spark plug in by hand. Then use a wrench to tighten the spark plug. Once the plug is tightened, reconnect the spark plug wire.

Clean or Replace the Air Filter

The air filter should be cleaned or replaced every 10 hours of operation. Access the air filter by removing the air filter cover. The cover on this model does not require tools to remove the filter. Some models have screws that must be removed.

The new foam filter needs to be oiled before installation. The oil improves the filter’s ability to trap dust before it enters the engine. To oil the filter, apply a small amount of clean motor oil to lightly coat the filter. Then squeeze the filter in a paper towel to equally distribute the oil and remove the excess oil.

Once the filter is oiled, reinstall the filter and cover.

Lubricate and Refuel

Pull the trigger to ensure the throttle is operating smoothly. If it doesn't spring back quickly, lubricate it with a little WD-40.

Refuel the trimmer with fresh fuel mix. Using a fuel mixed with fuel stabilizers helps keep the trimmer running trouble-free.

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