What is displacement?

Inside an internal combustion engine there is at least one combustion chamber where fuel is burned with air, to push a piston, which provides power. The volume of the combustion chamber that the piston moves through is called the swept volume. If you add together the swept volumes for all of the cylinders, you get the displacement for the engine.

Displacement is most often measured in cc which stands for cubic centimeters. A cubic centimeter is the same as a milliliter, so a 1000cc engine is also 1000ml, or 1.0 liter. Automotive engines are generally discussed in liters, but we use cubic centimeters for motorcycle engines, with the exception of bikes that are around 1000cc, which are sometimes called “liter bikes”.

What is horsepower?

Hopefully you should know this one. Power is the thing that pushes you forward when you twist the throttle. Because an internal combustion engine makes power by burning fuel, the power output of an engine increases with the engine speed (RPMs) because you get more explosions per second. Eventually either a limiter activates to stop the engine tearing itself apart, or there’s some other bottleneck. This gives an engine a power curve, with the stall speed at the bottom, the redline/limiter at the top, and peak power somewhere in-between. The quoted power of an engine is this peak power output.

The horsepower unit goes right back to the age of steam engines. One horsepower can lift 550 lbs, by one foot, in one second. The alternative unit of Watts or Kilowatts (W, kW) is becoming increasingly popular. One horsepower is equivalent to around 0.75 kilowatts, so a 75kW motor makes roughly 100 horsepower.

Does more displacement mean more horsepower?

Broadly speaking, yes. Here’s a graph showing the average horsepower for displacements for the bikes listed on Motorbimble. You can see that a bigger engine usually means more horsepower.

On average, you get about 1 horsepower for every 10cc of displacement, but there can be a lot of variation. 600cc and 1000cc bikes have a higher average because these are popular engine sizes for sports bikes, which will be tuned to maximize horsepower. For example, the most powerful bike listed on Motorbimble is the 310 horsepower 2019 Kawasaki Ninja H2 R which has a 998cc supercharged inline-four. For comparison, a 2020 Indian Scout Sixty is a cruiser with a 999cc naturally aspirated V-twin that makes just 78 horsepower, despite being slightly bigger.

These engines are designed for very different riders. The Kawasaki is a highly specialised sports bike - so you’ll be making lots of power and lots of noise when you’re on the track with the revs around 14,000. It’s engineered to get the absolute maximum power for the size of the engine. However, the Scout is for cruising on roads. You don’t need 200+ horsepower, so it only revs to around 7000. A smaller engine with a higher redline would give you just as much power, but you’d have to have the revs high and keep them there. Cruiser riders would rather have a bigger engine so that it makes the same power without having to wind it up.

How much power do I need?

Probably not as much as you think. If you’re new to biking, you should stick to something modest until you find yourself wanting more. It’s more important to find out what type of bike you enjoy riding.