Armstrong is an important name in British motorcycling, with a long and rather complicated ownership history. Brand names including BSA, CCM, Bombardier, Can-Am, Harley Davidson and CWH Developments are all intertwined in their history.
In 1981 Armstrong bought a majority share in Clews Competition Motorcycles (CCM); road racing and military motorcycles powered by Rotax engines were in production. CCM’s Rotax powered 250 machines began to be marketed under the Armstrong name with many top riders on board. The Armstrong racing division ceased production in 1986.
Rotax themselves shelved plans for a 350cc engine in 1981 when it became clear the International class was drawing to a close. Armstrong saw an opportunity and designed the CM36 – 347cc with magnesium bodied, power jet Dell’Orto carburettors and horizontally split crank cases.
This interesting 350cc Grand Prix motorcycle falls outside of the Post Classic racing period used today as it was produced for racing in 1982. Throughout our research we’ve received fascinating accounts from riders of the day, several of whom rode for Ruth Randle’s successful race team.
The 350 Armstrong was definitely manufactured in early 1982. It was completed just in time to be freighted to the 1st GP of 1982 in Argentina. Which if my memory is correct was in March.Jeff Sayle, 5th 350 World Championship 1980. Armstrong 250GP rider 1982.
Four machines were manufactured for Tony Rogers, Steve Tonkin, Clive Horton and myself. The machine had not even been started before we took delivery in Argentina. Two were freighted for Tony Rogers and myself to compete in the 350 World Championship. Tony and I also had a Armstrong 250 for the 250 World Championship.
When we started the machines we discovered a huge vibration problem, later to be found that the crankshafts had not been balanced. Even with these problems I managed to qualify 8th and Tony 11th. The race was less successful with Tony crashing early in the race and my machine vibrating itself to pieces, firstly the exhaust pipe blew out a huge hole in one an eventually the disc valves vibrated to pieces and the engine seized. The machine showed lots of potential running around 6th position before the problems began.
A funny side light to the vibration problem was after consulting with the engineer back at Bolton I was told to put sponge rubber on the handlebars, that might help with vibration!!!!
The next GP was in Austria at Salzburg and after having the crankshaft balance problem rectified the machines ran fairly well, both qualifying in the top 20 with Tony finishing 8th and myself 9th, we were in a dice for 6th to 10th, so a fairly positive result.
I did ride the IOM TT during this season , but the bike broke a conrod that went through the gearbox in Kirk Michael village (scary shit). This engine was destroyed an another set of crankcases made.
I believe the only victory the 350 took in 1982 was by Clive Horton at Brands Hatch short track in May, he also set the fastest lap although not a lap record, which I held at the time on a 350 Yamaha. At the end of 1982 I left the Randle/Armstrong team, so after this period I cannot help a lot, I presume the 350 would have been ridden in International meetings in 1983 as the World Championship ended in 1982.
I rode the 350 Armstrong in 1982 and 1983.Steve Tonkin, 1981 Junior TT winner on an Armstrong 250. British 250 Champion 1980, 1981, 1982
The 350 Armstrongs were first made around 1982 or 83 in a steel tubular frame and the first ones would have been run by Armstrongs themselves. The company did sell a batch of them a year or two later. The first riders on the 350 would have been Steve Tonkin and Jeff Sayle.Derek Huxley, Cotton Rotax works rider.
Armstrong then produced a carbon fibre frame around 1985 and raced them in the British Championship series with Donny Mcleod and Niall Mackenzie. Two years after the first carbon fibre frame Armstrong produced a second version which they raced in Grand Prix with the same two riders. There was also a Spanish rider who rode a 250 carbon bike at the end of the year Spanish races around 1988 or 89.
This is my recollection of the Armstrong 350cc parallel in line disc valve twin racing engine designed by Barry Hart.Clive Horton, 1977 British 125 Champion, TT winner 1974, Grand Prix rider.
Though promised in 1981, it didn’t see the light of day until 1982. It was very similar in layout to the increasingly popular Rotax twin of the time which was also similar to the very successful 250 and 350 Kawasaki that was winning most of the GP races since 1978.
The big differences being, the Armstrong 350 did not fire simultaneously on both cylinders, they were in fact 180 degrees apart. making the dynamic balance of the cranks quite difficult. They did overcome it, god alone knows how, Barry must have been quite a clever engineer.
This gave the engine a deceptively smooth feel when riding it as opposed to that distinctive punchy feel from the Rotax. It also had a wide spread of power delivery, often needing one less down change on many corners, saving precious time.
Quite wisely Barry utilised the Yamaha TZ gearbox, a reliable well made design, but using his own selector mechanism, manufactured in bronze if memory serves, but this should be verified by someone else before being taken as gospel. He also used TZ Yamaha Connecting rods, Big end bearings and shims, a very sensible choice.
The Clutch push rod operating mechanism was also made of bronze and, to my mind anyway looked a bit clumsy. It did however function perfectly.
The drawer backs as I recall were lack of reliability. The crank pins were prone to snap as they were a smaller diameter where they entered the flywheels. I loved the bike even so. It finished 1st, second or had a snapped crank pin, damnit.
A couple of years later when the engine manufacture was taken over for use in F2 sidecar racing the crank pin was modified with a small radius where the pin changed diameter and I was told, no longer a problem.
The engine was used by the Armstrong riders under the management of Chas Mortimer throughout 1984, 85 in the fantastic Carbon fibre framed machines designed by Mike Eatough to great success but not the world championship to which it deserved. The riders being Niall Mckenzie and Donny Robinson.
The above is accurate to the best of my knowledge and recall.
Regards Clive Horton
Inspiration from Austria, translation
The Armstrong 350cc although it is powered by an English engine, originated directly from the Rotax two stroke tandem twin engine. Alan Clews, the owner of CCM (Clews Competition Motorcycles) based in Bolton near Manchester began producing motocross machines and when Rotax began marketing their two cylinder rotating disc and liquid cooling machine in competition, Clews expanded his business to the racing machines.
Two important victories for the 250cc
In 1981 CCM was financed by Armstrong whose name was on the tank. Factory rider Steve Tonkin won the TT in the Isle of Man on the 250cc at an average of 106mph and an Australian rider Jeff Sayle took fourth place on an another Armstrong, Tonkin won the MCN Vladivar 250 championship followed by Sayle in second place.
Increasing the cubic capacity
Encouraged by these successes, Clews decided to move to the 350cc category and as Rotax was limited to the 250cc, Alan Clews, who already fabricated his cylinder heads and crankshafts, embarked on the construction of a 350cc. This construction was entrusted to Barry Hart who retained the 54mm stroke and raised the bore to 64mm to achieve a cylinder of 347cc. The Armstrong Team in 1982 composed of Jeff Sayle and Tony Rogers started out finishing 8th and 9th at the Austrian GP. Rogers then broke his leg at the French GP at Nogaro where Sayle finished 3rd. This was the best result for Armstrong finishing 9th in the 1982 championships without gaining any more points in this class, which was not re run in 1983.
Twin tandem, twin cylinder water-cooled 347cc (64m x 54m) – 75 ch/12000 tr/min – two crankshafts coupled by gears, powered by Dell’Orto rotary discs and carbs Ø 36mm or 38mm depending on the circuits. Motoplat electronic ignition, six speed Armstrong engine block box, chain drive, telescopic Marzocchi suspension, ar cantilever, Freins Brembo double disc, ar. single disc, magnesium wheels, 155 mph–100 kg.
The Armstrong-CCM 350cc entry at the 1982 championship was inspired by Rotax but built in England and ridden by Jeff Sayle.