# What does the 'cc' mean on a motorcycle?

I'm relatively new to motorcycles, my flat mate taught me how to drive his two Royal Enfields around New Delhi, and for the past year and a half I've been taking care of them as they break down ;)

Was just curious what the 'cc' actually means when you say a Hero Honda has 150 cc, or an Enfield as 350 cc, or a really beast Enfield has 500 cc. I know vaguely that more cc is more powerful, but am curious as to how one could actually measure cc.

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What happens when they rebore it.. It will change cc too..? –  user3732 Sep 21 '13 at 14:57

cc is the size of the engine, in cubic centimeters - literally the volume of the cylinders. A larger cylinder can ingest more air (and more fuel), thus converting more energy per cycle than a smaller one, so making more power - assuming all other factors are the same, and there are many factors that affect power output.

You can measure it by a simple volume calculation - area of the piston (pi x radius squared) x stroke x number of cylinders.

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Its worth noting that the size the bike is marketed as is rarely exact for example my Ducati Monster M600 (600cc) is actually a 583cc engine. –  Mauro May 14 '13 at 14:24
Indeed - the same is usually true of car engines - my 1.6L Honda is actually 1595cc –  Nick C May 15 '13 at 9:00

The "swept volume" of one cylinder is given by :

pi * r^2 * L

r = cylinder radius (bore / 2 ) in centimetres L = stroke in centimetres

Then multiply by the number of cylinders (they will all be the same bore and stroke)

Example : Bullet 350 bore and stroke given as 70 mm ( 7.0 cm) bore and 90 mm (9.0 cm) stroke So : r = (7.0 / 2) 3.5 cm L = 9.0 cm Then : pi * 3.5 ^2 * 9.0 * 1 (cylinder) = 346.3606 cubic centimetres Note : the capacity is usually rounded, in this case to 350 cc

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