One of my motorcycling buddies, who loves Harley, recently told me about his current build of a non V-twin engine. Our conversation moved to the differences between a v-twin and other types of motorcycle engines.
What is the difference between a v-twin, inline-4, thumper, parallel, and boxer? Four differences exist between a v-twin, inline-4, thumper. parallel, and a boxer. Among them are engine layout, sound, style of motorcycle and best application.
Similar to comparing superheros, picking the best engine will be subjective. That being said, we can still look at overall trends and application from the marketplace to help you pick the correct engine for your style of riding.
Here is what you need to consider.
Know The Kinds of Motorcycle Engines Are Associated With Manufacturers
On the highest level each kind of engine has been synonymous with different manufactures. If you are new to motorcycling, this might be the quickest way to identify each kind of motor.
Here is a table for each type of engine and manufacture followed by a more detailed discussion.
| ENGINE | MANUFACTURER |
| V-Twin | Harley & Ducati |
| Parallel | Various |
| Thumper | Japanese Manufacturers |
| Boxer | BMW |
| Inline-4 | Japanese Manufactures |
V-Twin: The V-twin engine has become the icon of American motorcycle manufacturer Harley-Davidson. Starting in 1903 the first three motorcycles were in fact single cylinder engines. Harley quickly moved to a V-twin design that it has become so well known for today.
The second famous motorcycle manufacturer is Italian-based Ducati. Their engines are more modern than Harley’s traditional air cooled v-twin.
When you look at the engine from the side, a distinct V shape will show up from the cylinders. This is how the name v-twin came into existence.
Moto Guzzi also mainly makes v-twin engines for their motorcycles. The engine sits differently into the frame than a Harley or Ducati. To see the V-twin shape of the cylinders, you need to stand in front of the motorcycle.
From here, you will notice the two cylinders poking out of each side of the bike. The engine sits in the frame the same way a V8 sits in an American muscle car.
Parallel: A parallel twin motorcycle engine has the cylinders running almost vertical. In most cases, the cylinders are also parallel to the down tubes of the motorcycle frame.
Many manufacturers have made parallel engines for motorcycles. The most popular models in terms of numbers come from the Japanese companies. England is the country that covets this engine. At least from a historical perspective.
Triumph, a British company, is the most synonymous with the parallel twin. If you look back on British motorcycle history and you will see the development of a special style of motorcycle called a cafe racer. We will talk more about cafe racers in a later post. For now, you need to know that Triumph has influenced the cafe racer heavily. One of the most popular style of engines is the parallel twin.
Thumper: A thumper engine is a single cylinder motor that produces lots of torque. Every dirt bike and four-wheeler (except for the Yamaha Banshee) are technically thumpers. There sound will be unlike any other motorcycle engine.
Some of the most loyal thumper fans come from the adventure riding world. The two most popular models include the Kawasaki KLR and Suzuki DR. Both of them are 650 ccs. KTM produces a few thumpers, but the brand has moved more towards a parallel style of engine.
One downfall to this engine is the emissions which they produce. In fact, many KLR fans note this factor as a reason for Kawasaki recently ending the production of this motorcycle.
Boxer: You will find the boxer engine unique when compared to all the engines in a motorcycle. As a motorcycle manufacturer, BMW is the most famous producer of boxer engines. While it is not the only engine they produce, BMW has made the best boxer engines for motorcycles.
The easiest way to recognize a boxer engine is finding large symmetrical extrusions from each side of the motorcycle.
The motor got its name from the opposing piston movement. When you watch a boxing match and see the punches flying back and forth, you know why the engine is referred to as a boxer. If not, search YouTube for a boxing match and watch it for a few minutes. You will see the fists flying back and forth.
What is a boxer engine? Boxer engines have cylinders that oppose each other instead of forming a V or that run parallel to each other. This design creates a better balance due to the side-to-side motion of the pistons.
Some riders I encounter state the boxer engine gives the smoothest ride.
Inline-4: In terms of production, more inline-4 engines exist than any other style of motorcycle engine. A rider will find one in just about every type of motorcycle from cruisers and standards to sport bikes.
While not a complete history, this engine has an interesting background. A few decades ago, the United States put tariffs and other controls on the kinds of motorcycles could be imported. Harley and other US manufacturers wanted to protect their market share by not allowing V-twin style engines. (I believe there was also some kind of limit on the number of large displacement engines the Japanese could import.)
To adapt and still get access to the US markets, Japanese companies started making more and more inline-4 engines. They were a popular engine for motorcycles from the 1970s and 1980s.
Kawasaki made my favorite inline-4 with the KZ line. I had a 1980 KZ 650 that I used to ride around town. This same motorcycle also started my annual fall ride. I also experienced my first set of highway pegs on this motorcycle. I thought they were great until I later experienced more comfortable pegs. I have a detailed post that outlines proper positioning of highway pegs and different pegs. I would still have my first set if I knew how to position them.
My first and only sport bike was a cousin to the KZ line. My sport bike was a GPZ 1100. It was also an inline-4. I rebuilt this bike only to have it drop two of the cylinders shortly after I installed a new motor.
As you can see, I have lots of memories of my inline-4 motorcycles. Most of them are cheap and relatively easy to maintain if you keep the oil changed.
DIFFERENT LAYOUTS OF MOTORCYCLE ENGINES
We went over the differences between the engines on a high level, now let’s get into a few of the technical differences between the engines.
V-Twin: I noted earlier the layout of a v-twin as an obvious V. Many differences exist between the angle for the cylinders. The crankshaft may have one or two pins.
The difference in the angle and crankshaft pins affects how much the engine vibrates and some characteristics of the engine. Harley engines are 45-degrees and have a single pin crankshaft. This creates monster torque, but you will find the motorcycle shakes and vibrates a large amount.
Harley has taken action to reduce the vibration by mounting the motors in rubber to help isolate the vibrations. Other manufactures have moved to changing the angle of the V between 60 and 90-degrees and added a second crankshaft pin. This reduces the amount of vibration and appeals to many riders.
In fact, non-Harley V-twins are much less intimidating to learn on or own as your first cruiser.
Parallel: As you can tell from what we have discussed so far, the parallel engine cylinders sit right beside each other. When comparing this to the V-twin, less room is needed for the engine.
The bike designer can also move the engine to the front or back of the bike to change the handling characteristics. This could help when performance is needed for braking and acceleration.
A rider will find two styles of parallel engines. The two have different feels to them.
The first has the two pistons on the crankshaft 180 degrees from each other. As one piston moves up the other is moving down. Effectively this creates a counter balancing effect so the engine will not tremble, shake, and vibrate as much.
The second parallel design has a crankshaft with one pin so both pistons are moving in the same direction at the same time. The cylinders alternate firing. Naturally there is more vibration in this configuration than the first design.
The motorcycle will feel more like a V-twin. I can remember the first time I heard of these motors off in the distance. The “Harley” like sound was off just a bit. My buddy told me it was a British twin. I did not believe him until the bike passed our location.
Thumper: A thumper engine will be the simplest design of all the engines we discuss.
There is only one cylinder. The name of this single-cylinder engine came about from the thump-thump-thump sound the engine makes as the RPMs increase.
Thumper diehards become critical of what an actual thumper is. Earlier, I described a thumper as just about any single cylinder motorcycle. Thumper enthusiasts add a point for a motorcycle to become a thumper:
- The motorcycle must be a large displacement. We talked about the KLR and DR 650 as two great examples. Both are larger on the displace scale. When we talk about displacement, really we are looking at the displacement on a per cylinder basis.
The cut off for large displacement is not clear. Some riders feel like a single cylinder 400 four-stroke motorcycle are large displacements. Based on the information and conversations I’ve been a part of, 500 cc’s seems to be the larger consensus.
We know thumpers for their high torque and are not fast motorcycles. This makes them great for specifics styles of riding that we will talk about later in this post.
Boxer: A boxer engine layout has the pistons opposing each other. We note a few of the characteristics earlier like the limited lean angle.
I should also mention the torque reactions of the motorcycle in a corner. Because of the rotation of the engine, when you go to lean the motorcycle over in a corner, the motorcycle may want to lean over more or stand up.
Leaning the bike over against the motor rotation will may it want to standup do to the rotational momentum of the engine. Likewise, lean the bike over the other way and it will want to lean over faster. You need to be careful of this will riding a boxer engine.
Inline-4: Add two more cylinders to a parallel and you have an inline-4 engine. The Japanese manufacturers made these models popular, particularly in sport bikes. They were also popular in the 70s standard and foreign cruisers.
You will find the best part of an inline-4 is the power delivery. The engine delivers horsepower smoothly and does not vibrate the way other engines do such as the V-twin. These engines crank out big horsepower at higher RPMs.
On the downside, the lower RPMs make the bike harder to ride because of the lower torque. A V-twin for example will allow you to chug away at speeds below 25 MPH in one gear. With an inline-4 you may need two or three gears.
A rider will also find the screaming nature obnoxious to get any power from them. If you ride sport bikes, this may not be a big deal.
You will also find the engine spills out of the frame with its extra width. Whereas most v-twins, parallels, and thumpers all sit within the frame rails. The extra width affects peg placement for forward controls.
The exhaust for an inline-4 reduces ground clearance. The exhaust ports are on the front of the engine making the header pipes rap down and around the front of the motor.
Different Sounds Of Motorcycle Engines
| ENGINE | SOUND | Sounds Like |
| V-Twin | Very Deep | Potato Potato |
| Parallel | Deep | Da Da Da Da |
| Thumper | Slightly Deep | Thump Thump |
| Boxer | Slightly High Pitch | A Tractor |
| Inline-4 | High Pitch | Hornets Buzzing |
What Is The Best Type Of Motorcycle Engine?
The long and short of picking the best engines centers on the riding you plan on doing. There is no one engine that fills every gap in every riding style. Check out the table below if you want a quick picture of the best engine. For a more detailed explanation read the description following the table so you know how to best apply the benefits of each engine.
| Engine | Best Application |
| V-Twin | Cruising |
| Parallel | Cafe Racer and General Riding |
| Thumper | Adventure and Dirt Bike |
| Boxer | Cruising and Adventure Riding |
| Inline-4 | Sport Bike Riding |
V-Twin: The torque of the V-twin make it the best motor for a cruiser style of riding. The lower speed and extra weight you carry from an additional person, or camping equipment make this the best style of engine.
The engines do not rev high (except for Ducati) and make riding on hilly roads a lot of fun. You should note though, cruisers are not always the best choice for your first motorcycle. In this post, I talk about a few reasons this is the case. (INSERT THE LINE FOR THE POST)
Parallel: Ahh, the iconic parallel! We talked about this engine as it relates to the British motorcycle scene and cafe racer style. After reflecting on all of this, I would argue the parallel is the best overall engine for general riding.
They are narrow and light making them great on curvy roads so you can flick the bike back and forth without sacrificing ground clearance. The light nature also makes them responsive.
For the manufacturer, the engine provides a relatively simple design so manufacturing is not expensive.
Thumpers: Low end torque and simple designs makes these engines appealing. Look at the prices of new and used bikes. You will find the simplicity makes them more economical. The simplicity also makes them easy to work on.
The low end torque makes these motors great for slower technical riding like what you find in off-road adventure riding, enduro, trail riding, and dirt biking.
Boxer: Smooth delivery and great balance make the boxer engine appealing. They are best suited for a shaft-drive motorcycle.
The nature of a boxer helps lower the center of gravity on the motorcycle. Riders will find these engines great for cruising and non-technical adventure riding. Specifically adventure riding on dirt and fire roads. When you get into trails, riding the width becomes an issue.
Inline-4: Enter the sportbike, high RPMs and high horsepower are the name of the game here.
These engines do best above 8000 RPMs and sound like a pack of mad hornets. Nothing else needs to be said as the popularity of these engines speaks for itself.
Weakness Of Each Type Of Motorcycle Engine
Now you know the best application for each style of engine and we have even discussed a few flaws for each of them. Let’s dig a little deeper into the weaknesses for the motors.
V-Twin: We talked about the vibration issues earlier in the post. The point is worth bringing up again simply because of the issues this causes. For example, I know some people who feel sitting on a v-twin at a stoplight is the same as sitting on an out-of-balance washing machine.
Personally, the biggest problem I have is my hands getting numb and falling asleep after a long time in the saddle. I combat this by stopping frequently.
The second problem with the V-twin is the difficulty cooling all parts of the engine. The cylinders sit almost back to back. Manufactures pay close attention and either water cool the bikes or create additional airflow around the back cylinder.
Parallel: Being able to do several things makes you not good at any one thing. They will disappoint people who want to focus on one style of riding. For beginners though, the parallel engine matches up great for the new rider. She will discover her preferences in the world of motorcycling.
The second flaw we already hit on is the vibration. This point largely depends on the configuration of the parallel design, alternating piston positioning or the same positioning.
Thumper: These engines have three challenges.
The rider first notices the vibration as there are no additional pistons countering the momentum. This feature also creates the great low-end torque.
Second, the engines do not create a large amount of horsepower. Do not look for these engines for high-speed applications.
The last challenge comes in the way of size. Cylinders can only get so big before you gain additional problems. Specifically, they use a lot of oil and start emitting unnecessary emissions.
Boxer: I mentioned the width twice now making riding in smaller areas (such as the woods) difficult.
The lower lean angles makes high speed turning a little more challenging too.
We also discussed the torque reaction above as the motorcycle turns.
Inline-4: You may ask, “Mad hornets? What could be weak about a pack of mad hornets?” The engine does not do as well riding in daily traffic. The engine is best suited for specialty applications and not as versatile as others.
Riders will find the engine wide as we noted earl lacking torque.
What is the best motorcycle engine? Reframe questions and start with your preferred riding style and then pick the engine to suit that style. Here you will find the best results enhancing your riding experience.
OTHER ODDBALL ENGINES
We did not get into the other motorcycle engines like flat-4, inline-6,
Boss Hoss V8, or triple. These models are just not a popular and would have made the article way too long. If you want to see something on these engines, drop me a comment below.