Let’s run through our ABCs of current-day mainstream big-bike manufacturers, shall we. Aprilia, BMW, Benelli, CF Moto, Harley-Davidson (Benelli!), Honda, Husqvarna, Kawasaki, KTM, Moto Morini, Norton, Royal Enfield, Suzuki, Triumph and Yamaha, every one of them either already has parallel-twin motorcycles on sale, or soon will.
While Ducati and MV Agusta are the only two big names that don’t, MV recently announced that it is working on a 350cc twin. A safe bet, it will place its cylinders in a line rather than a V. Things are no different back home, and it’s just a matter of time before Bajaj and TVS have their own twins based on the future models born of their JVs with foreign players.
So why has this engine format become so popular? The answer is a combination of factors, but the driving force is affordability. This is easily the most cost-effective way to make a twin-cylinder engine. Unlike a V or horizontally-opposed twin, parallel-twins use just one cylinder-head, which reduces the number of components needed. The quantity of materials required is lower too and that saves manufacturing costs.
There are also many packaging advantages because parallel twins can be very compact. This helps keep kerb weights down while also giving the designers more leeway with things like lower seat heights and better heat management. The customer also benefits through lower costs during major services, as there’s only one head to open and fewer materials to replace during valve-clearance services.
Another big reason behind the soar in parallel-twin popularity is that manufacturers have figured out how to make them exciting. Gone are the days where parallel-twins only existed in retro bikes or fairly bland middle-weight Kawasakis. Clever use of uneven firing orders, among other things, has resulted in motors that can quite closely replicate the sound and feel of a V-twin, while retaining the above-mentioned benefits of a parallel-twin.
For example, the angry motor in my 790 Duke is brimming with character. It sounds and feels almost like I’m riding a V-twin, but it’s also smoother, less cranky at low revs and doesn’t have a rear cylinder that’s constantly trying to cook me. I feel no desire for any other cylinder arrangement.
Of course, heritage goes a long way and it’s why manufacturers like Ducati and Harley-Davidson will always have thumping-great V-twins on offer. But there’s no doubt that we’re going to see more and more affordable parallel-twins, and some of them will be very tempting machines indeed. This holds especially true in a time where the world is going through unprecedented financial duress and the effects are going to be felt for years, if not decades. Purse strings will tighten up, but desires never go away, and a situation like that will only bolster the rule of the parallel-twin.