Outdoor power equipment with a 2-stroke engine has a number of advantages over equipment with a 4-stroke engine, but it also has special requirements.
Let's look at the pros and cons of 2-stroke engines, as well as how to keep them working properly and the best way to store them for the winter.
2-Stroke Versus 4-Stroke
When you purchase outdoor power equipment, the product's description will tell you if it runs on a 2-stroke or 4-stroke engine. A 2-stroke engine, sometimes called a 2-cycle engine, is one that completes a power cycle in two strokes of the piston.
Think of the piston as a disk or plunger inside a cylinder. As the piston moves up, it compresses a mixture of gas and air. At the top of the cylinder, a spark plug ignites the fuel, forcing the piston down. As the piston moves down, it uncovers a port on each side of the cylinder. The exhaust from the combustion is vented out one port, while new fuel and air move into the chamber through the other port. The up and down movement of the piston provides power to the engine.
A 4-stroke engine takes four strokes to complete the same actions: One stroke to compress the fuel followed by a return stroke; another stroke vents the exhaust and allows new fuel into the chamber, followed by a return stroke.
A 4-stroke engine has a system of intake and exhaust valves that are synced to the movement of the piston.
Four-stroke engines have separate lubricating systems. You add gas to one tank and oil to a separate tank - the two never mix.
In a 2-stroke engine, gas and oil must be mixed together to lubricate the moving parts in the engine. The ratio of gas-to-oil is determined by the equipment manufacturer, so check the owner's manual, but generally, the mix is about 4 ounces of oil for every gallon of gas.
Because there are fewer parts in 2-stroke engines, they tend to be much lighter than 4-stroke engines, making them good choices for any tools that need to be carried, like chain saws or string trimmers. They are also less costly to manufacture and repair.
But, there are drawbacks to 2-stroke engines. They are not as fuel efficient as 4-stroke engines, and because the oil and gas are mixed, they tend to produce more pollution. Two-stroke engines usually have some visible exhaust. They also burn oil quicker than 4-stroke engines.
Two-stroke engines work best on equipment that needs short bursts of power, like lawn mowers and chain saws. Four-stroke engines are better for large engines, like those on cars and trucks.
Tips for Winter Storage
Outdoor power equipment is typically used only part of the year. To make sure it will start up next season, it is important to make sure the tool is stored properly during the off season. Check the manual that came with the tool for specific recommendations.
For tools with 2-stroke engines, most manufacturers call for draining the fuel from the tool or adding a fuel stabilizer. These steps are necessary because the ethanol found in most gasoline can gum up fuel lines, gaskets and other engine components, and corrode metal parts if the gas is allowed to sit in the tool for two or three months.
Most manufacturers call for draining the tank if the tool will be idle for 30 days or more. Ethanol is not a problem in cars because people use up the gas in the tank quickly and because less oxygen can get into a car's fuel system.
Follow these tips to prep a 2-stroke engine for storage:
- To drain, empty the tank into an approved container. Try to start the tool to remove all traces of fuel.
- Remove the spark plug and add a tablespoon of 2-stroke engine oil to the spark plug opening.
- Place a rag in the opening and slowly pull the starter mechanism a few times to distribute the oil. If the spark plug is in good condition, reinstall it. If a new plug is needed, replace it before putting the tool in storage.
- Clean the air filter on the tool and tighten any loose nuts or screws.
- Clean off any debris on the tool.
- Store the tool in a dry place where children cannot reach it.
Unless you can use the fuel you drained from the tool in another 2-stroke engine immediately - remember, it is a mixture of gasoline and oil—discard it in a safe and legal manner. If you are not sure how to do so, contact your town or county for instructions on disposing of hazardous wastes.
If you decide to add fuel stabilizer, it is still a good idea to drain the existing fuel and fill the tank with fresh fuel before adding the stabilizer. That way, you can be sure that the tool will start up next season.
About the Author:
Fran Donegan is a power tools aficionado who writes on outdoor home equipment for The Home Depot. Fran is also the author of the home-improvement books Pools and Spas and Paint Your Home. To research Home Depot's motor oil selection online you can visit the company website.