Maintaining and operating four-stroke and propane turf maintenance equipment

Four-stroke equipment, such as this backpack blower from Dolmar, offers improved fuel efficiency over two-cycle units. Dolmar reports that fuel consumption is 40 percent lower and operating costs, based on 200 hours of operation, are 50 percent better.
Photo courtesy of Dolmar.

Two-cycle equipment has long dominated the professional turf maintenance equipment market, and there’s no shortage of those hardworking tools on lawn and landscape trailers. For various reasons, though, some professional LCOs have opted to try alternate power sources for their trimmers, blowers and other maintenance equipment. No matter the fuel source or engine configuration, proper maintenance and operation are important to ensuring performance in the field.

Going to four-stroke

Four-stroke turf equipment offers users accustomed to two-cycle models a different power curve, designed for more torque at the low end and more balanced power throughout. The way these four-stroke engines operate also provides maintenance benefits, notes Gary Bryan, product marketing manager with Dolmar. “A true four-stroke is more or less just like a car motor. It has an oil reservoir, so you’re not mixing the oil. So, the serviceability of it is more like a motor you’d see in a car or anything with straight gas.”

There are a few reasons that four-stroke engines tend to be longer lasting and lower maintenance, says Bryan. “Your RPMs aren’t as high as they are with a two-stroke, which revs higher to get the torque. Four-strokes don’t have to work as hard to get the torque,” he explains. Dolmar rates its equipment to run E15. “Traditionally, what happens with ethanol in a mix is that, if you’re not mixing a synthetic oil to help the engine run cooler, you have a possibility—especially in warmer climates and depending on how the operator is operating and maintaining the equipment—of burning that equipment up,” says Bryan. Because four-strokes are running at lower RPMs and run cooler, that danger posed by ethanol is less of a concern.

Bryan says there’s a difference between a true four-stroke engine and a “four-mix” piece of equipment, which incorporates the gas and oil together. “From what I’ve seen in the field, there’s a mental hurdle we have to get over, because four-mix equipment has been having larger service issues,” he states. These issues typically have to do with the frequent need to adjust valves, which is not the case with true four-stroke units, adds Bryan.

Dolmar offers four-stroke brush cutters, string trimmers, backpack blowers, hand-held blowers and 1-inch centrifugal pumps. The owner’s manuals state that after the first 20 to 25 hours, the oil should be changed. After that, oil changes are recommended every 50 hours. The next service—other than normal filter checks and changes—is not until 250 hours, when a valve adjustment is recommended. “That’s what is recommended, and that’s what you should go by. But, we’ve had units [go] longer than that. I’ve had sales reps tell me that they’ve sold units that have been used commercially for years without a valve adjustment,” says Bryan.

Four-stroke equipment also offers improved fuel efficiency over two-cycle units. Dolmar reports that fuel consumption is 40 percent lower and operating costs, based on 200 hours of operation, are 50 percent better. “The units will run longer on a tank, so the guys don’t have to go back to the truck as often to fill them up. Not only does it have longer run times, but because you’re not putting oil into [the gas] there’s a [cost] savings there, as well,” explains Bryan. “Four-stroke equipment also is much quieter, and the pollutants are much less, only 10 percent of two-cycle equipment.” That benefits the operator and the environment, he notes.

Not all manufacturers subscribe to the theory that turf maintenance equipment must use a four-cycle engine in order to perform well and run cleanly. Kawasaki manufacturers a number of four-cycle engines for use in mowers and other equipment, but Noah VanOosterhout, power product specialist with Kawasaki, says the company has intentionally stayed out of the four-cycle hand-held market. “The reason is that we’ve been able to make a two-cycle engine that’s clean and meets all the requirements for emissions, yet is still lightweight and extremely low-maintenance,” he explains. In particular, VanOosterhout says that with two-cycle equipment, there is no valve adjustment or maintenance necessary. “They are also much more tolerant of poor fuel quality, and they also are generally much more tolerant of different oils. The hybrid four-cycle engines on the market that still burn oil are extremely sensitive to fuel, and the manufacturers of that equipment only recommend very specific oils—often their brand of oil,” he says.

VanOosterhout says that when fuel gets older and degrades, it looses “light ends.” “The light ends are responsible for keeping the fuel system clean, and they also help allow easy starting. Two-cycle engines can usually run on poorer fuel, which has lost a little of the light ends, and it’s not going to affect it quite as much as with a four-cycle,” he explains.

Dennis Stauch, vice president of engineering at Makita, says that lowered emissions and noise, along with improved fuel efficiency, are the biggest reasons lawn and landscape professionals opt for four-stroke equipment. “Whereas the two-stroke fires every time the piston comes to the top of the cylinder, four-stroke equipment basically fires every other stroke, so the noise isn’t nearly as high-pitched or aggressive,” he explains. “Also, four-stroke engines are typically much easier to start. When you pull on the recoil rope, there’s much less force than with a two-stroke because you’re not pushing against the compression of the engine.”

Makita offers four-stroke string trimmers (blade capable), brush cutters, hand-held blowers and a 75cc backpack blower. Not only are these four-stroke engines easier to start physically, but they’re typically more likely to start easily than two-stroke engines because of the increased technology that had to be added to the latter to meet emissions requirements, says Stauch. “Four-stroke engines are less finicky to start and perform much better with the different types of ethanol blends in fuels out there. Two-stroke engines tend to be much more finicky. Our four-stroke engines will handle ethanol fuels much better,” he says. While four-strokes will work better than two-strokes with lower octane gases, Stauch says that any equipment will see improved performance with higher-octane blends.

True four-stroke equipment, such as that offered by Dolmar, offers increased low-end torque, as well as reduced maintenance requirements.
Photo courtesy of Dolmar.
Some of the primary benefits of four-stroke equipment include improved fuel economy and lowered emissions. Makita’s four-stroke backpack blower, for example, meets EPA Phase II, CARB Tier III requirements while offering a reported 53 percent longer run-time per tank than two-stroke blowers.
Photo courtesy of Makita.
With propane hand-held equipment, “You’re never getting any gumming in the carburetors; you’re never getting any residue or buildup in there, so you never have to worry about any of that,” explains Bernardo Herzer, CEO of LEHR, Inc.
Photo courtesy of LEHR.

Out in the field, Stauch points out that there’s not much difference between the maintenance required on two-stroke and four-stroke equipment. In both cases, air filters and spark plugs may need to be checked. An advantage of four-stroke equipment is there’s no need to rely on members of a crew to properly mix oil and gas, as is the case with two-stroke equipment. “On two-stroke engines, if you don’t mix the oil correctly you could have too much oil, which could lead to plugging of the muffler and exhaust ports,” he explains. Too little oil, obviously, could seriously damage or destroy the engine.

For servicing dealers or on-staff mechanics, four-stroke equipment maintenance is relatively straightforward. Stauch says, “It’s like opening up the hood of your car and checking the oil. Specifically on Makita products, you take off the plastic cover and it’s about a 10-minute operation to check the valves and then you’re good to go.”

He adds that four-stroke engines on turf maintenance equipment should be a natural fit for those working in the green industry. “Almost every single commercial landscaper has a four-stroke mower,” Stauch points out. “You have to check and change the oil. If you put your hand-held equipment into the same maintenance cycle as your mower, it’s a very easy transition from two-stroke to four-stroke.”

Propane power

Another option for professionals looking for alternatives to two-stroke equipment is propane-fueled units. One of the key benefits of propane is lower maintenance requirements. “You’re never getting any gumming in the carburetors; you’re never getting any residue or build-up in there, so you never have to worry about any of that. Using a cleaner fuel, you end up with a lot less buildup around valves,” explains Bernardo Herzer, CEO of LEHR, Inc. “With the increase of ethanol in gasoline to E15, there are even larger problems for small, air-cooled engines. Propane completely eliminates that.”

Another advantage, he adds, is that it is 110 octane. “By running a higher octane fuel, you can increase the compression and get that engine to run more efficiently, and that really is what you want,” says Herzer. Finally, he says, “Propane burns so much cleaner that it produces about 97 percent less particulates than a gasoline comparative, and about 96 percent less carcinogens. So you’re breathing in a lot less of that while you’re operating the equipment.”

Some lawn care pros might be concerned that the addition of a propane canister can make the equipment heavier, but Herzer says that’s not necessarily the case. “The container is about the same weight as a thick plastic container, and propane—even in a liquid state—weighs half as much as gasoline,” he explains. “A gallon of gasoline weighs about 8 pounds and a gallon of propane weighs about 4 pounds.”

Operators will notice other positives in terms of owning and maintaining propane-powered maintenance equipment, says Herzer. “The benefits of using propane is that you don’t have to choke it; there’s no priming. There’s also no winterizing necessary, which is a big plus.” Gasoline has a limited storage life, especially with the addition of ethanol, whereas propane canisters can be stored indefinitely, Herzer adds. The oil in propane-powered equipment requires less-frequent changes, as well, because there are fewer by-products building up in it, he adds.

LEHR offers propane trimmers, blowers and walk-behind mowers. As with any item powered by an engine, there is the need to occasionally service propane equipment. “It’s not very common in string trimmers, but after a certain number of hours, whether you’re running gasoline or propane, you want to check the clearances in the valves,” advises Herzer.

Four-cycle and propane equipment tend to operate more quietly, he says. “The fuel really doesn’t have that much to do with the sound of the equipment,” Herzer points out. Rather, it’s more how efficiently the fuel is burned that makes a difference.

Stihl offers a variety of hand-held equipment, including hedge pruners, brush cutters and blowers, powered by its 4-Mix engines, which combine benefits from both two-cycle and four-cycle engine designs.
Photo courtesy of Andreas Stihl Ag & Co. Kg.

Combined Efforts

While some manufacturers opt to build two-cycle equipment and others are focused on four-stroke power tools, it’s worth noting that some companies have designed engines that share some features of each.

Stihl, for example, says its 4-Mix technology offers “increased power, added torque and the benefits of two-stroke and four-stroke technologies combined.” This approach utilizes many of the elements of a four-stroke engine design, but, like a two-stroke engine, uses the same mix to provide both fuel and lubrication. This means that parts such as an oil pump, oil tank and oil pan can be eliminated, saving weight and making the engine more compact. Stihl reports that, “Lubrication by the fuel mixture also makes annoying, time-consuming service work—such as regular adjustment of the valve clearance, oil checks, oil changes and disposal of the waste oil—unnecessary” with its 4-Mix engines. The company also claims advantages in terms of emissions and sound. Decompression valves are used on these engines, making them start easier and faster. Stihl offers brushcutters, hedge trimmers, pruners and other equipment with 4-Mix engines.

Shindaiwa’s C4 Technology (Compression-Charged Clean Combustion) engines bring together the best elements of two-cycle and four-cycle engines. The company reports that its C4 Technology engines feature “a supercharger element to increase crankcase pressure. This ‘Power Boost Chamber’ element not only provides for increased power and torque, it also enables the use of standard mixed fuel for engine lubrication.” C4 Technology engines feature overhead intake and exhaust valves, and, like traditional four-cycle engines, produce four strokes of the piston for each power stroke. “But,” Shindaiwa notes, “without the complexity of a separate lubricating system, which must be frequently checked and monitored to avoid serious engine failure.” Finally, Shindaiwa says this design produces professional level power with less noise and lowers both noise and emissions levels.

Patrick White is a freelance writer and editor who has covered every aspect of the green industry in the past 13 years. He is based in Middlesex, Vt., and is always on the lookout for unusual stories.