The Ratier C6S was the second motorcycle built under the Ratier name, a 600 cc flat-twin with overhead valves made in France between 1959 and 1962. It was the modern half of a two-model range: where the 750 cc L7 still used side valves, the C6S had rocker-operated valves and was judged equal in performance to the BMW R60.
Ratier C6S at a glance
| Maker | Ratier, through RAM (Ratier Aviation et Marine), Montrouge |
|---|---|
| Production | 1959–1962 |
| Origin | Motorcycle business taken over from CEMEC, the former army workshop CMR |
| Engine | 600 cc flat-twin, derived from wartime BMW designs |
| Valve gear | overhead valves operated by rockers, C for Culbuté in the model name |
| Rear transmission | shaft drive with a rubber flector instead of a universal joint |
| Main customers | French police, army and the presidential escort |
| Benchmark | BMW R60, matched on performance |
| Earlier model | L7, a 750 cc side-valve flat-twin |
| Built | about 1,200 motorcycles in total, L7 and C6S together |
There is no Wikipedia page for the C6S: the facts come from the motorcycle section of the English article on the Ratier company, so this page is based on one source.
History of the Ratier C6S
Ratier built aircraft propellers at Figeac long before it built motorcycles. After 1945 the French army needed machines for police and garrison units and used the BMW motorcycles and patents taken as war reparations, with a semiprivate workshop, the Centre de Montage et de Réparation (CMR), refurbishing seized German bikes and reverse-engineering the parts it could not buy. The chief engineer Jacques Dormoy developed the design from there, and the motorcycle side of the business eventually passed, by way of CEMEC, to Ratier’s own non-propeller branch, RAM (Ratier Aviation et Marine) at Montrouge, where production restarted under the Ratier name.
The first fruit of that work was the 750 cc L7 with side valves. It was a simple engine of an old-fashioned kind and was soon regarded as an obsolete design, so the French Gendarmerie preferred to buy new BMWs from Germany. Ratier’s answer was the C6S, a 600 cc flat-twin with overhead valves operated by rockers — the C in the name stood for Culbuté, the French word for a rocker-operated valve train.
In practical terms the C6S matched the BMW R60. According to the surviving account of the range, the only real difference between the two lay in the final drive: the Ratier used a flector, a rubber coupling, where the BMW had a universal joint between the gearbox and the shaft to the rear wheel. Even so, official orders did not last. General Charles de Gaulle equipped his presidential escort with Ratier motorcycles, but most production went to the army and the police, civilian buyers were few, and the government declined to renew the contract. Only about 1,200 motorcycles were built in total, and the Figeac works returned to aircraft parts, which it still makes today, including for Airbus.
Design and features
- Overhead valves: the rocker-operated valve gear behind the C for Culbuté gave the C6S more modern breathing than the side-valve L7.
- BMW benchmark: contemporary accounts put the 600 cc Ratier on a par with the BMW R60.
- Flector drive: a rubber coupling replaced the universal joint in the shaft drive to the rear wheel.
- Official equipment: the army and the police took most of the production, and Ratier motorcycles served in de Gaulle’s presidential escort.
Ratier C6S versions
- C6S: the standard 600 cc overhead-valve flat-twin.
- Police and army versions: the bulk of the production, finished for official service rather than for private owners.
- L7: the earlier 750 cc side-valve model built alongside it.
The C6S followed the side-valve Ratier L7 in the range. Other machines from the same works are in the Ratier collection.
Sources
- Ratier, English Wikipedia: C6S engine and valves, comparison with the BMW R60, flector, production total, company history
