Here's an explanation of all the terms we use in the comparison matrix. Still got questions? Shoot us a note at info@rockmoto.com.
Engine size. Technically, this is the displacement of the engine, expressed in cubic centimeters. It’s literally the internal size of the engine. In general, the larger the engine, the more power it produces, and the more fuel it burns.
Engine configuration. Engines can be set up in a number of ways, depending on what the manufacturer hopes to accomplish. These are the configurations you’ll find in our comparison matrix:
- A single has one piston moving inside one cylinder. This is the lightest, most inexpensive way to make an engine. A single can produce a lot of vibration if the engine is large, because that one piston is going up and down without another cylinder for balancing. Almost all off-road and dual-purpose bikes are singles, because you want a light, nimble bike for dirt riding. Plus, a single can lower maintenance costs, since there’s only one set of valves and one carburetor or injector.
- A parallel twin has two cylinders set side by side, like a double pack of Pringles. Twins generally can rev higher and provide a little more power than a single-cylinder motor of roughly the same size. And they have a different, slightly higher-pitched engine character.
- A boxer or flat twin has two cylinders headed away from each other. Many BMWs use this configuration, which provides a low center of gravity and good air-cooling, and helps smooth out vibration.
- A V-twin is a classic engine configuration, going back to the early days of motorcycling, though there are highly advanced versions today. Manufacturers use different angles between the V, from 45 degrees for Harley-Davidsons to 90 degrees for Ducatis, Moto Guzzis and some Suzuki models. V-twins can be good for newer street riders because they tend to produce more torque at low rpm – this makes them a little easier to ride when you’re still working on your skills. And 90-degree V-twins have what's called perfect primary balance, which really smoothes things out at certain revs.
- An inline triple is found on more and more new bikes, like some Triumphs. With one piston providing balance for the other two, all in a row, triples can be very, very smooth-running engines. They offer a combination of high-revving power and narrow engine width, which allows for a more compact overall design.
- An inline four is like two parallel twins placed side by side: four cylinders all in a row. This is the favored layout for many sport bikes and race bikes, where maximum power is the goal. With smaller pistons and light connecting rods and valves that can move quickly, inline fours can reach a higher rpm than most twins. Spinning an engine fast is one great way to make a lot of horsepower, but since inline fours generally perform best at higher revs, you may be doing more shifting and clutch work to get the most usable power on the street.
- A V-four is like two V-twins side by side. A V-four can have the high-revving advantages of the inline four along with the narrowness of a V-twin. Some high-end motorcycles use V-fours, like the Honda Interceptor, and they’re also used a lot in MotoGP racing.
Fuel system. This is the way fuel and air are mixed before they’re ingested into the engine. Throughout the last century, most motorcycles and all scooters used a carburetor, an old-fashioned, purely mechanical device. But technology marches on, and computer-controlled fuel injection has become more common. It provides more accurate fuel delivery (better for meeting emissions regulations), and can provide great throttle response as well as automatically adjusting to different altitudes, which can be a benefit if you ride in the mountains. However, when you’re running low on gas, most carbureted bikes have a reserve that you can switch to on the fly – most fuel-injected bikes don’t, so you have to keep an eye on your low-fuel light and keep track of your mileage.
Transmission. Power goes from the engine to the rear wheel to the road through the transmission. Most motorcycles have manual-shift transmissions with five or six speeds. It works a lot like a car, except that the gears shift sequentially: first, second, third... up to the top gear. Unlike with a car, you can’t skip a gear. Some off-road and beginner bikes have a semi-automatic gearbox, which means there’s an automatic clutch. To shift, you just let off the throttle and toe the transmission to the next gear. Most scooters are fully automatic, usually with continuously variable transmissions. Some of these CVTs offer multiple automatic modes, such as a “normal” setting as well as a “power” option that spins the engine at higher rpm, giving you more speed. And some have push-button “manual” shifting that provides more control to the rider, like a standard transmission.
Final Drive. This is what connects the transmission to the rear wheel, which puts the power to the ground. Motorcycles and scooters with different purposes use different designs. To handle high power and keep overall weight low, the age-old, link-plate chain is king. But chain drives do eventually get messy and require regular maintenance, including cleaning, lubing and tightening. Another popular choice is the belt, typically a fabric-reinforced, rubber-toothed belt that’s nearly maintenance free. You’ll find the belt drive primarily on cruisers. Then there’s the shaft, used by many cruisers, sport-touring bikes, a lot of BMWs and some other European models. The shaft drive is completely enclosed. It’s clean and quiet, but also heavier and slightly more expensive to produce. Shaft drives are practically maintenance free, mostly requiring just the occasional oil change.
Seat Height. This is literally the distance from the top surface of the seat to the ground, in inches. But beware: Measured seat heights and practical seat heights can be two different things. When you’re sitting in a saddle, how much your feet are actually planted on the ground is based on the shape of the seat, its width, and the bike’s suspension. (A motorcycle with soft suspension will sag more under the rider’s weight, which lessens the distance from saddle to road.) Before you buy a bike, it’s important that you sit on it to see how comfortable you really are with both the height and the weight of the bike. Keep in mind, you don’t have to be able to plant both feet firmly on the ground to ride certain motorcycles, especially very lightweight ones. And if you aren’t particularly tall, you can work your way up to higher seats as your riding skills improve.
Curb Weight. Curb weight is the overall weight of the motorcycle when it’s ready to ride, meaning full of all the fluids you’ll need (gas, oil, etc.). Some manufacturers offer only dry weight measurements, which isn’t truly representative of the real weight of a ready-to-ride bike. In their test specifications, some motorcycle magazines feature wet weight measurements determined by calibrated scales.
Fuel Capacity. How much gasoline a motorcycle’s fuel tank can carry. More fuel capacity means you can ride farther between gas stops, but a bigger tank also means a heavier bike when you fill it up all the way. Fuel weighs a little less than six pounds per gallon.
