A Cleaner, Friendlier Engine

Two-stroke technology traditionally has been synonymous with hand-held power equipment, since it results in engines that are lightweight, powerful and inexpensive. However, the engines have their drawbacks: the inherent nature of two-stroke engines causes air pollution, both in terms of noise and hydrocarbon and nitrogen oxide emissions. The sound of a two-stroke engine echoing throughout the neighborhood is one thing, but with CARB and EPA Phase II emissions regulations, cleaner-running engines are quickly becoming a necessity.

Four-stroke engines provide an alternative, one that has been embraced by manufacturers such as Honda and Redmax. But four-stroke engines pose additional disadvantages – the technology costs more, and since the engines contain more parts, the resulting product is heavier. And, since landscape contractors must carry hand-held equipment during operation, extra weight makes a significant difference.

In response to the need for a clean-running, lightweight hand-held equipment engine, Honda recently introduced the GX25 mini-four-stroke engine, which weighs in at 6.1 pounds and features a cleaner system. “Our basic background is in four-stroke engines,” said Dave Haack, national sales manager for Honda engines, Alpharetta, Ga. “We know the advantages of four-stroke: cleaner emissions and thus better for the environment.”

Since two-stroke engines burn a mixture of fuel and oil, the combustion chamber is much harder to keep clean, said Joel Borowski, manager of technical operations for Honda engines. “You are bringing fuel in and out of the combustion chamber so quickly that you don’t get a clean burn,” he said. On the other hand, four-stroke engines feature a separate oil reservoir and only fire every other revolution, allowing for a clean burn and lower temperatures.

Despite being environmentally friendly, the Honda GX25 engine also claims to be more lightweight than other four-stroke engines, thanks to updated engine technology and lighter materials, Borowski stated. “We’re cognizant of the weight disadvantage,” he said. “Our overhead-cam technology has the cam shaft over the cylinder head, and we drive the cam shaft with a rubber belt, so it is quieter and lighter.”

Since the overhead-cam configuration incorporates the valve train into the oil reservoir, the overall weight can be compared to that of a two-stroke engine, and this setup creates a power-to-weight ratio of 0.29kW/kg. “We’ve used a lot of engineered plastics, which are lighter and quieter and just as durable as their metallic counterparts,” Borowski continued.

Another historical four-stroke disadvantage lies in a higher price tag. Although manufacturers have not yet been able to offer four-stroke engines at prices comparable to two-stroke engines, cost is not the most important issue to consider, said Sage Marie, power equipment public relations for Honda engines. “Something to keep in mind when talking about cost is the engine’s life expectancy,” he stressed. “Four strokes bring inherent value to the table because they, in general, last twice as long as their two-stroke counterparts.” This is because the four-stroke fires less often than the two-stroke, reducing temperatures and the resulting wear on the engine, he added.

Four-stroke engines also boast easy operation, Borowski remarked. The Honda GX25 features a 360-degree-inclinable feature, which allows the product to run and be stored in any position. Previous four-cycle engines have had a limited range as far as their angle of operation, he said.

Additionally, since the four-stroke engine runs on a pure gas mix, contractors don’t have to fuss with creating the gas/oil mix, as done with two-stroke engines. “Very rarely to people combine gas and oil well,” Marie admitted. “It’s hard to get that mix right, and having no fuel to mix is a big advantage.”

The true test for hand-held equipment occurs in the field, and Marie continued that along with reduced weight and clean emissions, the easy-start operation of the Honda four-stroke engine appeals to contractors. “Just one pull and this engine starts,” he said. “You don’t have to spin around twice and touch your toes.”

Currently, the most cumbersome obstacle to market acceptance of four-stroke technology is the preconceived notion of heavier operation, Borowski said. However, he hopes that as contractors test-drive the equipment and witness the benefits of four-stroke technology, weight will no longer be the prime consideration. “It’s the misnomer of it being heavier,” he said. “But with the increased life of four-stroke engines and the economy of use, we’re using that to get past the weight issue.” – Kristin Mohn

The author is Assistant Editor – Internet of Lawn & Landscape magazine and can be reached at kmohn@lawnandlandscape.com.