Is your trimmer due for a tune-up? Not sure how to work on the Mini 4 Stroke engine? Here’s what you need to do to keep your Honda string trimmer or brushcutter in top condition.
Maintenance Schedule
The first month or 10 hours: Change the oil.
Every 3 months or 25 hours: Clean the air filter.
Every 6 months or 50 hours: Change the oil, check the drive cable, check cooling fins
Every year or 100 hours: Check spark plug, spark arrester, fuel filter and fuel tank
Every two years or 300 hours: Replace spark plug
Every two years: Check fuel and oil lines, replacing as needed
Honda recommends getting a professional service every year or 100 hours. The technician will check the engine’s idle speed, valve clearance, and clutch shoes as well as lubricate the gear case.
Engine Oil
Used oil can be poured out of the filler neck, then added through the same opening. Using a syringe will make it easy to add the small amount of oil these engines need to stay lubricated. The 25 cc engine holds 2.7 fl. oz. (80 ccs) of oil, while the 35 cc engine holds 3.4 fl. oz. (100 ccs.) Honda recommends using 10W30 oil that meets API service category SJ or later.
Air Filter
To access the filter, close the choke to keep debris from entering the engine, then squeeze tabs on top of the cover and swing the cover down.
To clean the filter, wash it in soapy water. Once dry, place the filter in a plastic bag with about an ounce of clean engine oil. Knead the bag to distribute the oil, then squeeze out the filter to remove any excess oil. Wipe out the air cleaner box before reinstalling the filter.
Removing the Fan Shroud
The fan shroud is held on using a single bolt top-mounted bolt. It can be removed using either a 4 mm or 5/32 inch hex wrench. The shroud needs to be out of the way to access the spark plug, spark arrester and cooling fins.
Spark Plug
The plug can be removed with a 5/8 inch plug wrench. The electrode gap should be between 0.024 and 0.028 inches (0.60-0.70 mm). Replace the plug if it’s fouled or has signs of electrode or insulator damage. If you’re reinstalling a used plug, turn the plug 1/8-1/4 turn once seated. If you’re installing a new plug, turn ½ turn or torque the plug to 8.8 ft-lbs. (12 Nm) to seal the crush washer against the engine.
Cooling Fins
The surface of the engine block should be cleaned occasionally to remove dirt that can reduce heat transfer. Use a brush or cloth to wipe down the fins.
Spark Arrester
The arrester is built into the opening of the muffler and is held in place with two 6 mm screws. Once removed, scrub off any carbon deposits on the underside of the arrester with a wire brush. If the arrester mesh is cracked or has holes, it needs to be replaced.
Throttle Cable
Check the condition of the cable and the action of the throttle lever. If the lever doesn’t move smoothly or there is visible damage to the cable, the cable should be replaced.
There should be between 1/16 and 1/8 inch of free play when moving the throttle lever. If the cable is too loose, adjust the throttle cable tension using the adjuster next to the carburetor. Loosen the 10 mm lock nut, which is the nut closest to the carburetor. Turn the adjusting nut, located on a clamp opposite of the lock nut, to adjust the free play. Once the throttle play is correct, tighten the lock nut.
Fuel Tank and Filter
To clean these parts, remove the fuel filler cap and pour the gasoline into a fuel can. Use a piece of hooked wire to snag the fuel tube and pull it out of the tank. Inspect the fuel filter on the end of this hose. If it’s dirty, clean it with a non-flammable solvent. Replace the filter if it’s damaged or excessively dirty. To clean the tank, rinse it out with a non-flammable solvent. Once everything is clean and dry, push the filter and tube back into the tank.
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