Key Differences Between A 180-Degree And 270-Degree Parallel Twin 

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Summary

  • Parallel twin engines are becoming more popular due to their simplicity, cost-effectiveness, and versatility in various motorcycle frames.
  • The two main configurations of parallel twin engines are 180° and 270°, referring to the crankshaft angle and firing order.
  • A 270° parallel twin offers a more direct throttle response, smoother vibrations, and a throatier exhaust note compared to a 180° parallel twin.


The days of inline-four screamers are coming to an end, thanks to emission norms. Four-pot screamers produce excellent power and a smooth riding experience but are expensive to produce and not the best for the environment. On the other hand, V-twins are fun but difficult to package in a short wheelbase chassis. And boxer twins are niche and thumpers — no one likes thumpers, except the KLR 650.

This leaves manufacturers with parallel twin engines. These engines are simpler in design, cheaper to design and manufacture, and produce tractable power that can be used in the real world, not only on the track. Plus, these engines are compact and can be fitted in a variety of frames without much hassle. But these parallel twins come in two popular flavors: 180° and 270°. What do these numbers mean, and why should you care about them? Here’s everything you need to know about different parallel-twin configurations.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from the manufacturers and other authoritative sources, including Car Throttle.

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5 Reasons We Love Inline-Four Motorcycle Engines (And 5 Reasons Why Parallel Twins Are Better)

One is practical, the other is fun

180° vs 270° Parallel Twins: Inner Workings

When it comes to parallel twin engines, a few variations exist, but today, the only two that most bikers need to know are 180° and 270° parallel twins. So what do these degrees indicate? They refer to the crankshaft angle within the engine; simply, it’s how the pistons fire compared to one another. Let’s get into them.

180 Degree Crankshaft Explained

A few years ago, the most common type of parallel twin engine was the one with a 180° crankshaft. Here, the crank pins are located at the opposite ends of each other, i.e., at 180° from each other. So, when one piston is at Top Dead Center (TDC), the other piston will be at Bottom Dead Center (BDC), and when one rises, the other falls.

This comes down to the firing order of the engine. In a 180° parallel twin, the first cylinder fires, the crankshaft rotates 180°, and then the second cylinder fires. When the first cylinder completes the power stroke and enters the exhaust stroke, and that is when the second cylinder fires. Then, the first cylinder enters the intake and compression strokes before firing again.

Since we’re talking about four-stroke motorcycles here, there is a massive firing gap in the engine, giving the engine an uneven firing order. The second cylinder enters the power cylinder 180° after the first cylinder, and the crankshaft needs to rotate 540° before firing again. As a result, the firing order of a 180° parallel-twin engine is 180°-540°-180°.

270 Degree Crankshaft Explained

On the other hand, you have the burbly 270° parallel twin, which has recently become the most popular type of parallel twin engine on the market. This configuration is also referred to as a crossplane crankshaft engine; yep, the Yamaha one. Like the 180° parallel twin, the cylinders are situated side-by-side, but the firing order is completely different.

In a 270° parallel twin engine, the first cylinder fires, the crankshaft rotates 270°, and then the second cylinder fires. So, when the second cylinder fires, the first cylinder has only completed half of its exhaust stroke. For the next combustion within the engine, the first cylinder needs to cover the second half of its exhaust stroke (90°), followed by intake and compression strokes.

As you can see, when one piston drops, the second piston follows it three-quarters of a rotation behind. This gives the engine an uneven firing order of 270°-450°-270°. However, the interval at which both cylinders fire is smoother, resulting in a much better and more direct throttle response. Plus, the firing order is less uneven than a 180° parallel twin.

  • Kawasaki Ninja 400 and Z 400
  • Kawasaki Ninja 650 and Z 650
  • Honda NX500, CBR500R, and Rebel 500
  • CFMoto’s 400, 650, and 700 series

The Difference In The Real World

If you thought the above section got a bit technical, you’re not alone. Mathematics isn’t our strongest suit, either. So, let’s take a look at what these two configurations of parallel twin engines bring to the table on the road — what these differences mean when you ride your motorcycle.

Power Delivery

One of the most important aspects of a motorcycle is power delivery; lazy power delivery is boring and frantic is fun — think a Honda Gold Wing vs a KTM 890 Duke! In most cases, a 180° parallel-twin offers a more linear power delivery, and in this configuration, peak power and torque are delivered high up into the rev range. These bikes are more high-revving but may feel a bit dull in the mid-range.

On the contrary, a 270° parallel-twin offers power delivery that’s similar to a V-twin engine — both have essentially the same firing order. So, peak power and torque are delivered in the mid to high range, after which they taper off into the redline. As a result, these engines don’t rev as high but offer a more eager and lively power delivery, which is arguably more fun on the streets.

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The battle of the twins

Throttle Response

Power delivery and throttle response are closely related to each other, but don’t confuse the two. The latter refers to the way the engine reacts to your throttle input. Here, 270° parallel twins are the better choice. This is because this configuration essentially eliminates inertial torque. What’s that, you ask?

In a 180° parallel twin engine, the crank pins are located on the opposite ends of each other, so the crankshaft slows down when both the cylinders hit TDC and BDC after each stroke. This phenomenon results in the engine feeling “heavier” or offering a slightly dull throttle response. 180° parallel twins are also prone to rev-hang sometimes. On the contrary, 270° parallel twins eliminate this since the cylinders do not reach the TDC and BDC at the same time, resulting in a more direct throttle response.

Vibrations

Let’s get one thing straight: parallel twin engines are vibey and can never be as smooth as an inline four. With that out of the way, a 180° parallel twin is usually the more vibey one of the two configurations. This type of parallel twin produces a rocking couple, which can be eliminated with a balance shaft, but you will still feel it, especially if the engine is a stressed member of the frame. There’s also a lot of nitty-gritty about primary and secondary vibrations, but let’s leave that for physics lectures.

No surprise here, but 270° parallel twin wins here. The forces from the two pistons cancel each other out partially, so the vibrations aren’t as bad as the 180° crankshaft. The engine still vibrates, but manufacturers use a balancer shaft to eliminate them. And unlike the 180° parallel twin, this engine does not have an unbalanced rocking couple. The result is a pleasant buzz across the rev range that you will feel but won’t be bothered by.

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Exhaust Note

The three differences mentioned above are technical, imperceptible to novice riders, and not deal breakers. However, the soundtrack is what affects people’s buying decision when it comes to choosing between a 180° parallel-twin motorcycle, like the Kawasaki Ninja 650, or a 270° parallel-twin motorcycle, like the Yamaha YZF-R7.

Thanks to the uneven firing order of the 270° parallel twin, which is similar to that of a 90° V-twin, the exhaust note is throaty and pulsing. This is why some parallel-twin engines sound like V-twins. On the other hand, 180° parallel-twin engines honestly sound like lawnmowers or high-revving thumpers. The former is the clear winner here, no doubt about it.

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There’s more diversity than you might realize when it comes to the motorcycle powerhouses

  • Royal Enfield Interceptor 650, Continental GT 650, and Super Meteor 650
  • Yamaha YZF-R7, MT-07, and Tenere 700
  • Aprilia RS 660 and Tuono 660
  • Honda Africa Twin
  • KTM 890 Duke and 890 Adventure R
  • Norton Commando 961
  • Modern Triumph Bonneville Range

Don’t Forget The 360° Parallel Twin

Kawasaki W800
Kawasaki

Before 180° parallel twins were all the rage, 360° twins ruled the automotive market across the world. In this engine, the pistons move up and down at the same time with an even firing order. The first cylinder fires, the engine rotates 360°, then the second cylinder is fired; the firing interval is 360°-360°-360°. This results in a smooth engine, but the soundtrack, throttle response, and traction aren’t the best.

Wait, how is traction affected by the firing order? Thank you for asking. An uneven firing order gives what is known as a recovery gap in traction since the power delivery is pulsing. On the other hand, if the firing order is even, the power is delivered constantly without any pulsing, so the wheels don’t have time to recover from any traction loss. This is why V4 engines with their uneven firing order blast out of corners much better than inline-fours, except for the Yamaha R1, which uses a cross-plane engine.

  • Kawasaki W800
  • Norton Commando
  • Old Triumph Bonneville
  • BMW F 800 GS
  • BSA A65

Pick Your Flavor (We’d Pick A 270°, Though)

2024 Aprilia RS 660 on the track
Aprilia

Let’s address the ant in the room; if you love the Kawasaki W800 or classic British twins, you probably don’t care much about throttle response, power delivery, and vibrations. In that case, a 360° crankshaft shouldn’t be an issue. But if you like modern motorcycles that are enjoyable to ride and sound great, you need to pay attention to the type of engine your next motorcycle has.

As it stands, motorcycles are moving into parallel twins, and picking the wrong one will only make you hate these beautiful engines even more. So, if you prefer a tractable yet high-revving and sporty parallel-twin motorcycle, pick a 180° parallel twin motorcycle. But if you prefer more mid-range grunt, better cornering, and a burly exhaust note, don’t pick anything other than a 270° parallel twin motorcycle.

Parallel Twin Sports Bike Performance Comparison: Kawasaki Ninja 400 vs Aprilia RS 457

Specs

Kawasaki Ninja 400

Aprilia RS 457

Engine Type

180° parallel-twin

270° CP2 parallel-twin

Displacement

399cc

457cc

Compression Ratio

11.5:1

TBA

Max Power

44.3 HP @ 10,000 RPM

47.6 HP @ 9,400 RPM

Max Torque

27.2 LB-FT @ 8,000 RPM

32 LB-FT @ 6,700 RPM

(Specs sourced from Kawasaki and Aprilia)

In the end, always ride the motorcycle you want to buy. Theory may say a hundred things, good and bad, about a particular engine, but if it tugs at your heart, down the drain goes physics. Pick a motorcycle that you enjoy riding, even if it’s got a 360° parallel twin, a lazy boxer twin, or a thumper.

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