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Weed eaters, also called trimmers, are marketed with 2-stroke and 4-stroke gasoline engines. Each has its supporters, but generally speaking weed eaters with 2-stroke engines are cheaper, lighter and more powerful than eaters with 4-stroke engines; they also make more noise, vibrate more, emit more pollution, wear out more quickly, and you have to mix oil with the gas. Evolving EPA pollution requirements favor 4-stroke engines.
The term “stroke" refers to the movement of the piston in the cylinder of an engine. In a 2-stroke engine, compressed fuel explodes, pushing the piston outward; fuel is inserted into the cylinder as the piston returns. A 4-stroke engine has separate strokes for compression and exhaustion. A distributor on a 4-stroke engine supplies a spark every second turn of the crank shaft when the piston is close to the top dead center of the compression stroke.
- Weed eaters, also called trimmers, are marketed with 2-stroke and 4-stroke gasoline engines.
- A 4-stroke engine has separate strokes for compression and exhaustion.
Fuel and Power
You have to mix about 4 oz. of oil for each gallon of gas for 2-stroke engines. Two-stroke engines deliver more power for their size than weed eaters with 4-stroke engines; they are also more difficult to start than 4-stroke engines.
The simple design of 2-stroke engines means they are cheaper to manufacture, so the cost is less to the consumer. The oil that you mix with the gasoline in a 2-stroke engine can be expensive, plus 2-stroke engines use more gasoline than 4-stroke engines.
Two-stroke engines do not have a separate lubrication system as more sophisticated 4-stroke engines do; they rely instead on oil mixed with fuel, so their moving parts wear out faster than those in 4-stroke engines. This means they are more expensive to maintain. If you add too much oil to the fuel mixture of a 2-stroke engine, the engine will become sluggish and smoke will belch from the muffler. If you don’t add enough oil, your engine will run hot and can burn out.
- You have to mix about 4 oz.
- If you add too much oil to the fuel mixture of a 2-stroke engine, the engine will become sluggish and smoke will belch from the muffler.
Part of the mixture of air and fuel in a 2-stroke engine leaks out through the exhaust port as it is loaded into the combustion chamber. This is one source of exhaust emissions in 2-stroke engines that are a source of concern for the Environmental Protection Agency. The EPA discourages 2-stroke engines, which it considers heavy polluters, and encourages 4-stroke engines, which pollute less.