Elsewhere on the site I have discussed the lightweight belt-drive FN single, introduced in 1907. This model had only a brief existence, to be replaced in 1909 by the first shaft drive FN single.
In several respects the 2 1/2 hp, 224 cc single was ahead of the contemporary four. Both valves were mechanically operated, and the transmission featured a 2-speed gear and cone clutch. Otherwise the specification was similar to the four, although the overall build was much lighter. This model ran largely unchanged through 1911, with detail changes to the clutch (now multiple-plate), carburettor, and a capacity increase to 247 cc.
For 1912, a new model was announced. Longer, lower, and larger (285 cc), the single's development paralleled that of the four. Notable improvements were a separate rear stand and carrier, one-piece tank and detail changes to the controls.
By the outbreak of war, the pedals had gone in favour of a bevel-drive kickstart, and it was this model that reappeared when production recommenced following the hostilities. Again development paralleled the four: as the 750 side-valve four spawned the 750T overhead-inlet four, so the 285 spawned the 285T with an overhead inlet valve.
By 1923, the FN single - despite its
impressive specification - was really a bit behind the times. Performance-wise at least.
When the 346 cc unit-construction chain-drive M60 appeared for 1924 to replace the
shaft-drive single, its performance was good. Good enough even to signal the beginning of
the end for the heavier, more complex and far more expensive-to-build four.