Have you ever wondered why there are so many different types of motorcycle engines, and what makes one kind of engine so different from another? We go through everything from big thumpers to boxer twins to outrageous inline-sixes, and explain all the strengths and weaknesses of each, in this Motorcycle Engine Guide!
The internal combustion engine doesnat get any simpler than this; one big cylinder thumping away to create power. Simple in operation, cheap to produce, and easy to repair and maintain, single-cylinder engines lend themselves to use in economy motorcycles and scooters, and have powered millions of budget bikes the world over.
But thatas not the only place theyare at home; the thumping power pulse and good bottom end torque of a big single is also ideally suited to dirt riding. Virtually every dirt bike and many dual sports also run on single-cylinder engines, affectionately called athumpersa for the pounding vibration and sound they create.
- Virtually all dirt bikes and supermotos
- Most dual-sports
- Economy bikes like the Honda CBR300R
- Light and narrow
- Mechanically simple
- Good bottom-end torque
- Serious vibration; require a larger flywheel and the use of balancers to counteract it
- Almost always create a lower power to weight ratio than multi-cylinder engines of similar displacement
- Not suited to larger displacements
When you think of a twin-cylinder motorcycle engine, your mind probably goes straight to the aBig Twinsa that power most American cruisers. But you canat forget about the compact and economical parallel twin (or inline-two cylinder) engines that are characteristic of many bikes in history, such as the signature mill that powers the Triumph Bonneville. But the parallel twin is not just some relic; fast revving, high-performance versions of this engine configuration also power the sporty Kawasaki Ninja 300 and the even sportier all-new Yamaha R3.
- Many lower-end sport bikes
- Iconic cruisers and standards
- BMW dual-sports (F650GS, F800GS)
- Narrow and light
- Easy and relatively cheap to manufacture
- Good for general riding and commuting
- Noticeable vibration (can be worse than in comparable V-twins)
The most iconic and recognizable motorcycle engine, especially here in the States, is undoubtedly the V-twin. With two big cylinders oriented in a aVa pattern, the aBig Twina engine powers virtually every American cruiser (and even many Japanese ones.) The thick powerband, off-the-line torque, and most of all, the signature V-twin sound have been the keys to the V-twinas persistent popularity through the decades.
V-twins generally put out less power than similar-sized inline-4 counterparts, though they make up for it with the brute torque inherent to the V-twinas architecture. But V-twins can be fast too; just look to Ducati for inspiration about what a performance-tuned V-twin can do. The Italian sport bike manufacturer has been building and racing high-performance V-twins for a long time, and is cranking out an incredible 205 HP from the engine in the new 1299 Panigale.
- Virtually all American cruisers
- Virtually all Ducatis
- Mounted transversely in Moto Guzzis
- Plenty of torque and a wide powerband
- Low center of gravity
- That unmistakable V-twin sound!
- Can have vibration issues (especially in narrower V-configurations)
- Difficulty cooling the rear cylinder
- Create less power per unit of displacement than 3 or 4-cylinder engines
If youare looking at a boxer twin in a motorcycle, more than likely youare looking at a BMW; the odd-looking engine layout has been a signature part of the German manufactureras motorcycle designs for the better part of a century. The boxer twin is perfectly balanced, smooth, and delivers gobs of torque across the entire powerband.
Itas from this unique engine layout that the ubiquitous BMW GS, the most popular bike with a boxer twin, gets its ability to atractora its way through the toughest terrain in the world; those two big cylinders thump out enough torque to get the 600-pound bikes through just about anything, even at just above idle. It may not be the sexiest-looking engine ever put in a bike, but the boxer twin certainly has its strengths.
- Perfectly balanced, and a low center of gravity
- Linear powerband and smooth power delivery
- Perfectly suited to shaft-drive motorcycles
- Wide and unwieldy
- Limited lean angle
- Torque reaction on motorcycle in corners
The perfect middle ground between torquey twins and revvy inline fours, the triple is not traditionally one of the most popular engine architectures a but those who ride them swear by them. Triples are a mainstay of Triumphs model lineup, powering all of their sport motorcycles, and are gaining in popularity in models such as the new Yamaha FZ-09.
While triples donat typically boast the same high horsepower numbers of inline fours or the grunty torque of big twins, they are a great balance of both, making them perfect for everything from commuting around town to aggressive track riding.
- Perfect balance of characteristics of twins and inline fours
- Versatility; work well in all ridings situations
- Unique exhaust sound
- Narrow and compact profile
The smooth, fast-revving, extremely popular inline-4 is a universal engine architecture that powers most sport bikes you can think of. Since its introduction on the iconic Honda CB750 in the late 1960s, the inline-4 grew in popularity among the Japanese manufacturers for its ease of production, reliability, and good performance.
Today, they power virtually every Japanese sport bike, and the vast majority of road racing bikes in any supersport or superbike class in the world. Sport bike riders love the inline-4 for its smooth power delivery, screaming high revs, and the exhilarating top-end rush most performance inline-4s deliver.
- Most sport bikes, especially from Japanese manufacturers
- Simplicity and popularity of engine architecture
- Smooth power delivery
- Cranking out big horsepower, especially at high RPMs
- They need to scream; most are tuned for higher-end power
- Torque is not their strong point
- Can be a little wide
While the triple can be considered to be the ideal amiddle grounda between twins and four-cylinder engines, another unique a though somewhat more costly a middle ground between those two designs is the V-4. The complexity and cost associated with manufacturing V-4s keeps OEMs from putting them in anything but higher-end models, but those that ride with them love the smooth power delivery, high performance, and narrow profile. The best part about V-4s is probably their unique sound; as essentially half of a V8, they have a unique, throaty growl that is pure performance.
- Smooth, torquey power delivery
- High performance
- Narrow profile
- Incredible V4 sound
- Complex and expensive to manufacture
- Often heavier than comparable inline-4s
Unusual Engines Worth Mentioning
An unusual, impractical engine choice for a motorcycle, the inline-six has no logical place in a motorcycle a unless itas for a manufacturer to show off a feat of engineering (or an owner to show off at bike night.) The inline-six powered Honda CBX was not the only bike ever with an inline-six, but is the most iconic. The Kawasaki Z1300, produced from 1979-1989, sported an even bigger inline-6 powerplant.
The flat-4, with four cylinders arranged in opposing pairs (like a pair of boxer-twins) is best known for powering the original Honda Gold Wing, the GL1000. This architecture allows for excellent balance, plenty of torque, and a low center of gravity, but is expensive to manufacture.
Add two cylinders to the flat-4 and you get the flat-6, which powers the GL1000s big brother, the GL1800 Gold Wing. Like the flat-4, the flat-6 is torquey, has smooth power delivery, and has a low center of gravity, and is perfect for a big touring bike like the Gold Wing.
One of the most unusual production engines ever built, the oval-piston V-4 in the Honda NR, a wildly expensive production racer built by Honda in the 1980s, was and still is a marvel of engineering. Hondaas engineers attempted to capitalize on Grand Prix rules that required a maximum of four cylinders by making a avirtual V8a, with four oval shaped cylinders, each one with two connecting rods and 8 valves. The unique engine never translated to success on the track a but it sure is neat to look at.
What’s your all time favorite motorcycle engine, and why?