The Motorcycle "two-bank" Design
A very rare type of W engine is found in motorcycles of the MotoGP class. These are two-stroke, 500 cubic centimetres (30.5 cu in) V engines with two banks of two cylinders and two separate crankshafts, one per bank of cylinders, thus constituting a sort of "W" form. The angle between the banks varies from 60 to 75 degrees.
There are two major advantages of this engine over the more traditional inline-four engine or V4 engine. The first is the width of the engine: a V4 engine will be narrower than an inline-four engine with the same displacement, but a W4 with its two crankshafts will be even smaller. The second advantage is that the W4 lacks the need for a balance shaft; it will run smoothly if the two crankshafts rotate in opposite directions. This is a weight advantage over the V4 engine, which will need a balance shaft.
Examples of this type of W4 engine drive the Yamaha YZR500 and the Cagiva GP500 motorcycles.
This type of engine should not be confused with the U engine, which also has two banks of cylinders and two crankshafts, but which is made by combining two similar straight engines. The U engine lacks the advantages the "W" form of the engine has in terms of width and weight.
Read more about this topic: W Engine
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