From the launch of the inclined-cylinder BSA Sloper, critics claimed it a less efficient engine than if it had been built with its barrel vertical. This thought ignores the fact that sloping engines had been used in the motorcycle world for almost 30 years by the time the first Slopers hit the showrooms, and all V-twins have at least one and usually both barrels sloped. Then what about horizontal, aero and upside-down units? Essentially, if the carburation and – in the case of four-strokes – lubrication are appropriate, then engines will perform to expectations.
As often happens in such cases, negative observations have the reverse effect hoped for by critics, which, along with the sarcasm of comments such as BSA Sloper riders were posing ‘Promenade Percys,’ probably enhanced sales. What was strange, was that rivals soon witnessed BSA’s sales success, often at the expense of their own, yet dallied for up to half-a-decade before launching their sloping engine models, by which time the BSA Sloper was more than halfway through its production run.
While rivals were worthy in the eyes of many, they didn’t hit the spot in the way the Sloper did. This may have less than to do with their styling and more the timing of their launches. Among the examples, are machines from Ariel, Matchless, New Imperial and Triumph – the first two were marketed for a few years while New Imperial and Triumph may have influenced post-Second World War models.
Ariel
Despite – or perhaps in spite of – the hard-pressed times, Ariel was hell bent
