G80CS memories
I really enjoyed the story in OBA 56 on the Matchless G80CS, a model that has always interested me. I recall coming home one Saturday evening around 1960 just as ABC TV was, rarely for those days, and in black & white, showing Dave Curtis on a G80CS giving a riding lesson to the BSA team in the British Scramble Championship. I’ve never owned a G80CS, but in the early 1970s I bought a new G85CS engine from the late Stanley Phelps (Stan Rodwell), which he sent out from UK in several parcels. The crankcase had no numbers stamped on it, suggesting it was taken from spare parts. I fitted it into a rigid Matchless frame to use in Short Circuit (Dirt Track) and Long Track events. First time out was the Morgan Mile, and after a poor start, the engine came on song, rapidly hauling in a BSA B50 until my hastily-made exhaust system fell apart. My next event was a Short Circuit, where its power characteristics were unsuitable on the tighter track, so I foolishly had the cams modified to “scramble” specs by the late Laurie Wilson. It was better for Short Circuit, not so Long Track. I raced it through to the early 1980s, when through family commitments I sold it to the late Jack Powell of McLaren Vale, who had a collection of engines, and it is still owned by his son Kym.
An unusual feature of it was that the spark plug, although vertical in the head, was not central, as the plug hole finished in the same place as the roadster with its angled plug. Did they have cracking trouble with the G80CS with limited metal between spark plug slot and valve seats? Finally, your story states that the G80CS engines still had only the bronze bush on the timing side crankcase. In the Pearson “Single Cylinder Matchless” book, by F.W. Neill (AMC Service Manager), it states, under “1956-60 Scrambles Engines”, “a large roller bearing in conjunction with a short bronze bush forms the timing side axle bearing”. Which is correct? I’ve had many happy times, on and off road, with AMC motorcycles. May they live on!
Trevor Henderson Christie Downs, SA They certainly did have a problem with cracking cylinder heads on the “central plug” engines. The heads also suffered from poor gas flow from the inlet port angled to the right side, and many were welded up and re-machined as a “centre port” to permit a straight inlet tract, which also meant a direct passage to the centrally fitted air filters that were used on the later Metisse models. Regarding the timing side bronze bush, I believe this remained until the advent of the G85CS engine with the Norton gear-driven oil pump which replaced the old worm drive pump in heavily strengthened crankcases. In defence of this system, designer P.A. Walker told The Motor Cycle, “The use of a plain bearing is dictated by the method of oil transfer to the crankshaft assembly. The bush is heavily shouldered at the flywheel end to permit the use of a tight fit at this point, since a tight fit is impossible where the bush is cut away.”