What are “two-strokes” and “four-strokes” and how do they differ?
“Two-stroke” and “four-stroke” refers to different engine designs. Two-stroke designs are used in lawn mowers, chain saws, and other small, light-weight engines, while four-stroke designs are used in automobiles and just about everywhere else.
The practical difference is that two-stroke engines are designed to burn oil along with gasoline, so you need to periodically add oil. You may need to pre-mix the oil and gas, or the scooter may have a separate oil tank and a mechanism to do the mixing inside the engine.
There are very few two-stroke scooters that meet the new emission standards, so you’re unlikely to purchase a new scooter with a two-stroke engine. This is because the design of two-stroke engines results in unburned gasoline (and partually burned oil) being emitted in the exhaust.
On the plus side, two-stroke engines are simpler, less likely to break, and easier to fix than four-stroke engines. Modern manufacturing techniques have improved the quality of all engines, however, so you don’t really need to worry about this with a modern scooter.
For more technical info about two-stroke engines, read Howstuffworks: How Two-stroke Engines Work.
