Suzuki Rethinks Motorcycle Design

Patent applications often allow unprecedented insight into the projects underway behind the scenes at R&D departments of motorcycle firms, and while this one isn’t likely to point to a specific new model it’s fascinating to see that even the most basic elements of a motorcycle’s layout are still being reconsidered. It’s the latest patent application to come from Suzuki, published via the Japanese patent office last week, and it illustrates an interestingly simple way to potentially improve a bike’s packaging.

The design is intended to be used on single-cylinder bikes or those with inline engines, and revolves around the idea of flipping the entire engine and transmission into a different position. As can be seen here, the cylinders now run nearly horizontally between the main frame rails, with the crankshaft at the back and cylinder head nestled up behind the top of the fork. The transmission hangs below the engine rather than sitting behind it, and the cylinder head is reversed, allowing the exhaust headers to point downward.

What benefits are to be found by doing it like this?According to the patent application, there’s a twofold benefit: The layout allows for a shorter wheelbase, improving handling, while simultaneously making room for a longer swingarm. That should improve stability and reduce geometry changes during suspension movement.

The shorter wheelbase emerges because the layout gives more space for the front wheel to move backward as the fork compresses. That extra space is marked “S” in the patent drawing. Meanwhile, thanks to the new position of the crankshaft, countershaft, and output shaft, the swingarm’s pivot point can be moved significantly farther forward, giving a much longer swingarm overall.

Husaberg employed a similar layout in its 2009 to 2012 570 models, though the thinking for that layout was for moving the engine's crankshaft closer to the bike's center of gravity, rather than shortening the wheelbase.

As an additional benefit, the engine/transmission unit doesn’t hang as low under the frame as a conventional bike’s, leaving more space for the exhaust silencer to be packaged underneath, in the bellypan.

While the idea seems good, the patent clearly throws up a few questions. First, it seems better suited to a single-cylinder engine than a multi-cylinder; the chassis will need to be much wider just behind the steering head to allow the engine to be positioned like this, and on a four-cylinder it could simply end up being too wide, restricting steering movement. Second, while the patent mentions that the idea is based around a water-cooled engine, the illustration doesn’t show where the radiator will go. Side-mounted radiators could be the solution.

The design also requires other components like the airbox and fuel tank to be repositioned. According to the patent, the airbox and engine intakes take up the entire area that’s normally used by the fuel tank, designated “43” in these drawings. As such, the fuel tank also has to be moved, in this case to an under-seat position (40). The bike’s battery and electronics sit under the front of the seat (42). Storage space is sacrificed, as there’s no room either under the seat or in front of the rider.

While we’re not expecting to see a production bike using this layout anytime soon, we’ll be keeping an eye open for any further patent applications that expand upon the idea further.