Just in case we think that horsepower wars and the quest for more power is a modern concept, let's go back to the turn of the last century. In the late 1800s, bicycles were competing with horses, then the bicycles got engines clipped on to really compete with horses, then they gained the power of a team of horses. Imagine 6 horsepower ! It is as if someone today introduced a machine with the power of 6 cars !! In the quest to get even more powerful, single cylinder engines were traded for twins. This doubled power in many cases and created smoother engines. By the early 1900s, more cylinders were being recruited by many manufacturers, which ultimately resulted in production configurations of up to 16 cylinders in cars, and up to 8 in motorcycles. However, a hundred years later, some configurations have persisted while others have faded away.
Today, almost all motorcycles are 1, 2, 3, or 4 cylinders. The four cylinder powerplant is usually thought of in conjuction with revolutionary bikes from Japan. Indeed, you can argue that the inline four is what has ruled the performance wars for the last 40 years. However, the start for the inline four goes back to 1904 and a Dutch company. FN (Fabrique Nationale de Herstal) was a relative latecomer as a bicycle manufacturer, as their primary business was small arms. In 1904 FN built a four cylinder motorcycle which also had a shaft drive, and a five bearing crankshaft. This was truly revolutionary stuff. The first engines were 362cc, and featured a straight inlet manifold along with a rather unique distributed oiling system. Many other manufacturers followed suit, and the four cylinder became a standard format. Between 1905 and 1910, displacement gradually increased to 498cc while spark plugs, the carburettor, and exhaust were all moved. I have been able to see 2 of these early FN machines in museums (Solvang and the Petersen), and they are great examples of the craftsmanship prevalent at the time. Metalwork and plumbing were first rate, and the machines were elegant. However, with an unsprung front fork in the early machines, you wouldn't want to ride one too far, much less across Europe on 1904 roads, as was done to promote and prove the bike !
A later front suspension FN. It is interesting to note that the Czech brothers Laurin and Klement produced a 570cc four cylinder motorcycle in 1904 as well. It was named the CCCC, and was introduced at the Vienna show that year. Part of the reason for this motorcycle receiving less of the credit for being first is that it was simply a series of four single cylinder engines mounted in a bicycle frame. A four cylinder motorcyle yes, a four cylinder motor, no.