Shop Talk: Preventive maintenance for small engines

Talk small preventive maintenance practices with manufacturers and several main themes get preached to you over and over again.

The first preventive maintenance practice OEMs stress is that you take the time to inspect small engine-powered equipment every day. “If there’s a problem, stop and fix it,” says Scott Mack, senior training specialist with the Kohler Company. That may seem obvious, he notes, but many operators try to work an engine through a minor problem and end up with a catastrophic failure on their hands. “Timely repair is more important than getting any single job done that day and will reduce downtime and repair costs,” Mack stresses. He also recommends putting one person in charge of daily inspections rather than assuming operators are taking care of these matters.

Part of that daily inspection is checking the oil level. “Read the owner’s manual and follow the service intervals listed,” says Steve Forslund, senior engineer at American Honda Motor Company’s Power Equipment Division. “Make sure to use the right American Petroleum Institute viscosity rating, which is found in the API ‘doughnut’ on all oil containers.”

Kohler’s position is that synthetic oils are approved for use after the engine has seen an extensive break-in period. “But we recommend owners observe the same change intervals with synthetic oils as with non-synthetics,” says Mark Vande Slunt, manager of field service with Kohler. “Because of this there’s probably no advantage in using synthetics in our engines and doing so may increase overall operating costs.”

You need to make sure the air cleaner is in good condition, Vande Slunt adds. The engine will pull in air from somewhere, he explains. And if the filter is blocked it will pull in air – and airborne contaminants – from around the throttle shaft. While you’re at it, Vande Slunt says to check the stud seals on the air filter structure itself. They’re as important as the face seal between the filter and the canister.

Don’t try to save money by getting more hours from an air filter than it’s intended to provide. “It’s OK to gently knock a filter against a hard surface to loosen debris,” says Vande Slunt, “but don’t use compressed air to clean it. Water droplets in the air stream will perforate the filter media.”

Beyond the basics
Once you’ve got a handle on the basics, Mark Nelson, technical service representative for Briggs & Stratton Commercial Power, says you’re ready to get into some of the finer points of small engine preventive maintenance. “Don’t overlook other periodic maintenance,” he advises. “Changing the air filter and the oil are just part of the overall maintenance process. Be sure to also check and replace the spark plug as required. Check the engine’s valve clearance at least once per season. Also check the engine’s top, no-load operating speed at least once per season.”

Forslund notes that operators will sometimes tinker with the throttle control linkage, attempting to coerce a little more power out of the engine. “They think a faster-running engine is more productive and that they’ll finish faster,” he explains. “What gets finished faster is the engine, though small engines are designed to run at peak performance in a small window of engine speed. Forcing them to run faster can severely cut into engine life.”
That peak performance window also means running an engine below its optimal RPM and that is potentially damaging, Mack says, since low-RPM operation reduces fan speed and can cause overheating.

Briggs & Stratton’s Nelson likes to add some additional tasks to an engine’s daily inspection procedure. “Check the entire fuel system for leaks or missing parts,” he advises. “Visually inspect the muffler body, deflector and the spark arrestor, if the engine is equipped with one. With a manual starter, check the rope, grip and starter operation. With an electric starter, check the battery for charge condition and whether there are any leaks present. Inspect all cables and terminals. Check that safety interlock switches are functioning properly.”

Keeping small engines clean
Air-cooled engines rely on free air flow over their cooling fins to maintain proper operating temperatures. Our sources all recommended compressed air for cleaning debris out of cooling fins (with another one of those standard instructions: Wear your safety glasses when using compressed air!).

But pressure washers are at hand for many operators, and compressed air may be less accessible. Or they may be using the pressure washer to clean up the entire piece of equipment, so they pressure wash the engine, too. This ushers in a host of problems. High pressure water can pack debris more firmly into cooling fins rather than blowing it out. High pressure can force water past seals into engines and drive train casings, although Forslund and Mack both say this isn’t as likely today as it was before modern seal designs came into wide use. High pressure can also remove decals with warnings and other important information.

Forslund says a garden hose has enough pressure to clean an engine, and there’s no need to blast equipment with 3,200 psi of water. No matter what water source you use, though, he has three pieces of advice: First, let the engine cool completely before hitting it with water. Cold water on a hot engine will cause engine parts to contract rapidly and that can pull water inside. Second, keep the spray away from the intake side of the engine. And third, run the engine after washing it until it’s completely dry.

Tips on fuel for storage and high production
Mack and Vande Slunt suggest using fuel stabilizers all year, not just for storage. “Studies indicate that the regular use of stabilizers reduces engine deposits,” Mack says. “It’s important, however, to use the right amount of stabilizer. Take the time to measure it accurately.” When using a fuel stabilizer for storage, be sure to run the engine long enough that treated fuel is drawn into the entire fuel system.

Again, both Mack and Vande Slunt recommend that fuel be used within 30 days of purchase partly because gasoline is unstable and partly because modern gasoline comes in season-specific blends. Fuel additives are designed to alter performance characteristics depending on the weather, and using the wrong gas for the season can cause problems. “Winter fuel can cause vapor lock in summer,” says Vande Slunt, “and summer fuel can cause hard starting in winter.” He also recommends the use of plastic, not metal, fuel cans because they are less likely to form rust from condensation on the inside as the temperature changes.

Build a dealer relationship
Our sources encourage owners to develop a good working relationship with their dealers, and most owners understand the value of doing so. But how, exactly, is this done?

“Make regular visits to your dealer,” Vande Slunt says. “And stay consistent with your business and the machines in your fleet.”

He also recommends using OEM products instead of will-fit parts. “All OEMs argue against the use of aftermarket parts,” he notes. “We have no control over how those parts are manufactured and no way to confirm that they meet our standards, no matter what their manufacturer claims. But part of the value of paying for OEM products is that you’re building your relationship with your dealer, and that’s a good thing to do.”

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