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Understanding CCs

Simply put, "cc" is shorthand for cubic centimeter. When you are doing research to buy a motorcycle, you will see the term "cc" plastered on the tank or frame of every bike out there, along with a number: 250 cc, 500 cc, 750 cc. It won't take long to make the connection that a bike that has more cubic centimeters has a bigger engine, will produce more power, and will go faster.

Road-legal motorcycles, scooters, and even mopeds can have two-stroke or four-stoke engines ranging from 50 cc to more than 2,000 cc. But this doesn't explain what a cubic centimeter is or what it actually has to do with the engine.

Cubic centimeters measure the volume of a three-dimensional substance, such as a liquid or a gas. Or in this case, both: You are dealing with the volume of fuel mixed with air that powers motorcycles. Make a cube that's one centimeter long (0.39 of an inch), and you'll have one cubic centimeter.

What does this have to do with the size of a motorcycle engine? And why does a higher number of ccs on the tank translate to a faster motorcycle shooting down the highway?

This brings us to the concept of displacement, which is the stuff of science class discussions―and which a mechanic can discuss with you in depth. Displacement measures how many cubic centimeteres of the air-fuel mixture moves through one rotation of an engine cycle (each piston moving from top to bottom). For example, if one rotation of the pistons moves 125 cc of the fuel-air mixture through the system, then you have a 125 cc engine.

Now, 125 cc of fuel mixture, when ignited in the engine, will combust with a certain amount of force and propel the motorcycle with a certain amount of power. In an engine with a displacement of, say, 250 cc, more fuel will combust at once and more energy will be released.

On the other hand, a higher-displacement engine will burn more fuel, the bike will weigh more (and therefore need more power to go fast), and other considerations. But generally, a motorcycle with a higher engine displacement (measured in cubic centimeters) will have more power, being able to propel more weight and at faster speeds.