Over the past few years we have all seen the slow death of the inline-4 supersport. This is largely down to noise and emissions restrictions around the world getting more strict.
Supersports are also the first displacement to be affected by this – the canary in the coal mine if you will – signalling the beginning of the end for the internal combustion engine (ICE). To keep these engines in toe with emissions restrictions, means restricting them to such an extent that producing them no longer makes sense from a performance standpoint.
This is where the parallel twin steps in. An engine configuration that is naturally more efficient, in terms of thermodynamics (where singles are limited), power output, fuel efficiency and noise levels. Which is deeply ironic, because the p-twin has been around for as long as the motorcycle itself!
Long History Of The Twin
To look back at the history of the parallel-twin is to look back at the history of the motorcycle itself. The very first mass-produced motorcycle used one all the way back in 1894.
Along the way there were several tweaks and changes, and by the 1930s Triumph came out with their iconic 360 degree parallel twin. It proved to be a huge success for the manufacturer – even if the first motorcycles were not – and would lay the foundations for the British motorcycle industry at large.
By the 1960s Japan worked out that the whole 360 degree thing was inefficient, so they found a way to balance the 180 degree engine more effectively. The “rocking couple” was born and you will find this configuration used in several modern motorcycles, from little 200cc commuters all the way up to 1000cc ADVs.
The Modern Twin
Both the 360 and 180 degree configurations have obvious limitations. The 360 degree parallel twin is essentially a glorified single, especially early versions that used the “wasted spark” ignition system. The 180 degree configuration allows the engine to rev higher, but also has limitations and requires a balance shaft to be used or the vibrations become intolerable.
For many years it was accepted that the ideal configuration should be 270 degrees, as this would theoretically be more – although not quite perfectly – balanced, it would also mimic other desirable characteristics of a 90 degree V-twin. Unfortunately forged cranks could only really be produced flat, so the whole concept was effectively shelved up until recently.
Today, manufacturers are able to forge 270 degree cranks in a cost effective manner, and are some of the most efficient engines on the market. Able to balance performance characteristics with efficiency in a way other engines simply cannot. It is an elegant engineering solution, but it isn’t the only alternative p-twin configuration. KTM, as is customary with the brand, offer another variation, and their number is 285.
Is 285 Really The Magic Number?
We now live in an era where ICE motorcycles are approaching maturity, the technology to create highly optimised engines not only exists, but it is cost effective when mass produced. While 270 degrees is highly effective, it isn’t actually the only angle… so to speak.
KTM enthusiasts will argue that the reason why 790s and 890s make more power is because of this unique configuration. In reality, it is just a different way to achieve the same efficiency and performance results. Simply put, 270 degree cranks mimic 90 degree V-twins and 285 degree cranks mimic 75 degree V-twins. Guess who makes 75 degree V-twins.
It would also be pretty easy to say that because 270 degree cranks are more affordable to produce than 285 degree cranks they must be the better option. But, this argument doesn’t hold much water because KTM found a way to make their engines pretty cost effective… by sending production to China. In the same breath, quality then comes into the equation.
The reason why most 270 degree engines have proven more reliable, isn’t so much to do with the construction, but the tune of the engines. One ride on any stock CP2 equipped Yamaha will reveal the fact that it is an under-stressed engine, especially when you compare it to a “Ready-to-Race” KTM equivalent that wants to rev all the time.
So in a word, no, 285 is not a magic number. Unless you are in the KTM marketing department, because just by being different they got a whole lot of free publicity.