There’s a high chance that your small or lightweight motorcycle has an inline or parallel twin-cylinder engine. While some Suzuki models and Italian manufacturers may have favored a V shape, the straight twin motor was responsible for the post-war 1950s British motorbike boom. It is currently experiencing a resurgence in modern times.
What are Parallel Twin Motorcycle Engines?
Parallel twin motorcycle engines are commonly used for internal combustion engine configuration. As the name suggests, They are made of two cylinders that are parallel to each other. The pistons of each cylinder work together, driven by the crankshaft. The Parallel twin engine configuration provides smooth operation, balanced power supplies, and small dimensions.
Parallel twin bike engines are well known for their torque feature, which offers good low to mid-range power. They are commonly used engines as they are simple, affordable and easy to maintain. Due to their narrow profile’s improvement in dynamics and aerodynamics, they are popular in various types of motorcycles, including sport, naked, and adventure bikes.
Parallel Twin Engines: Pros
- Smoother than a one-cylinder engine but less expensive and complicated than a V-twin.
- Small and light in weight.
- Flexibility in performance.
Parallel Twin Engines: Cons
- Not as potent as larger V-twin or four-cylinder engines.
- Vibratory prone.
- No connections to athletic success.
Parallel Twin Motorcycle Engines: History
The straight twin engine had a successful start. It was used to build Hildebrand & Wolfmuller, the first mass-produced motorcycle, in 1894. It was faster, had smoother power delivery, and cost less to construct than the V-twin or flat-twin alternatives compared to a single-cylinder bike.
Power
The 1937 Triumph Speed Twin 5T made incredible use of parallel twin power and torque. Triumph, BSA, Norton, Arial, Matchless, and AJS all produced four-stroke twin-engine British motorcycles for three decades due to the bike’s popularity and its 27bhp, 498cc engine. The decline of parallel and inline twin motorbikes didn’t happen until Japanese manufacturers with three, four, and even six-cylinder engines in the 1970s.
Racing
The sole exception was in racing for smaller motorcycles, where Kawasaki adopted a tandem twin design for the KR250 and K350; the latter won four world championships from 1978 to 1982. This design used a crankshaft for each cylinder. The Rotax 256, used by motorcycle manufacturers, including Aprilia in 1985’s 250cc Grand Prix racing, also had the same tandem configuration.
Changing To The Middle Range
The straight twin gained a reputation as a modest, everyday engine as broader, faster in-line-four cylinder power and larger capacity Italian V-twins took over the more desired end of riding.
They were chosen for the everyday commuter bikes available from every manufacturer because they were compact, straightforward, and inexpensive to make. The disadvantages included increased vibration compared to alternatives and the fact that little progress was made to advance technology.
Because of this, the parallel and inline twin is called “humble.” It has found a home in various popular motorcycles in India, including the Honda CBF500 and the Kawasaki ER-6n that you may have previously driven during a Direct Access test. Along with the contemporary classic Triumph Bonneville, it also drives the BMW F800S and GS line.
The parallel twins also powered the Honda CB250N and CB400N Super Dream. These models were geared toward older riders or those considering a contemporary café racer custom. The 250cc Honda generated a similar 27bhp 40 years after the Triumph Speed Twin. The more powerful variant generated 43bhp and 103mph top speed. Although not the most thrilling bike ever made, it is incredibly popular. Especially considering that until legislation changed in 1983, beginners could ride any bike with a capacity under 250cc.
Regaining Strength
One reason is that many large single-cylinder bikes are being phased out due to stricter pollution regulations. Additionally, a general decline in the global economy has led to manufacturers sharing the same engine and parts across several motorcycle models, a strategy similar to that of automakers.
Because parallel twin engines are affordable and adaptable, it is easy to integrate them into bike designs. It may be readily converted from a cruiser application with lots of torque to a high-revving sports machine by altering the final ratio. Additionally, because the engine is significantly smaller than a V-twin, it may easily fit into various motorcycle chassis.
270° Crank
The famous 1995 TRX850 is responsible for the last justification. Although it wasn’t a big seller then, it was the first motorcycle in production to have a 270° crank. The 180° or 360° crank was a feature of older twin-cylinder motorcycles, without détails. Both produced power like a single-cylinder motorcycle, with the 360 design firing faster to compensate for the imbalance.
You may effectively simulate the V-twin engine feel and sound by using a 270° crank. Thus, you benefit from smooth power delivery while also enjoying the dual layout’s cost, weight, space, and maintenance advantages.
The Triumph Thunderbird and Thruxton 1200, the current Honda Africa Twin, CB500 and NC700 ranges, and the Royal Enfield Interceptor 650 all use 270° parallel twin engines. To emulate the Austrian company’s 75-degree V-twins, the KTM 790 Duke also uses a similar setup, while Yamaha has returned to the twin for MT-07 platforms, joining the Kawasaki Z250-650cc range.
