Layout: A bank of four cylinders running in-line with each other. Benefits: Smooth power delivery and fantastic peak performance.
The Americans were huge fans of longitudinal inline-four configurations, but it was Flemish arms manufacturer FN that was first to produce an inline-four in Europe back in 1905. Pre-1920s, a great many companies opted to try the stretched engine layout, including Indian, Excelsior, Henderson and Cleveland.
In the UK, Wilkinson (the forerunner of Wilkinson Sword) produced an 850cc model with this configuration called the TMC. The onset of war saw restrictions kill off production in 1916.
Vauxhall dipped into the bike world when it commissioned the production of six luxury prototype motorcycles in 1922. In the end, only two were built.
When people refer to inline-fours now, they typically mean across the frame fours (transversely mounted, not longitudinally), such as Honda’s 1969 CB750. But it was the Italian manufacturer GRB that produced the world’s first transverse four in 1923. The GRB technology eventually worked its way into Gilera’s hands years later, via bike producer Rondine, the technology eventually going into the firm’s Grand Prix winning across-theframe fours in 1948.
From that time on, transverse layouts have become the mainstream four-cylinder configuration, owing to their ability to cool all four cylinders equally and being able to run shorter wheelbases than their longitudinal siblings.