Clews Stroka was the original name for the English motorcycle later named Clews Competition Motorcycles or CCM. CCM motorcycles like the 1974 1/2 500 GP replica pictured here were the last gasp of four stroke English MX bikes. Born out of the collapse of BSA?s Competition Department in 1971 these machines went on to hold up the English four-stoke banner through the 70?s.
 Classic good looks to make a YZ426 envious. Much polished alloy, chrome frame with a "works" hand machined look! |
Alan Clews, founder of CCM, was a successful Trials and Scrambles rider in the late 60?s on home-built Ariel trials bikes and various English engined Rickman Metisse Scramblers. But Alan wanted a lighter, more nimble and modern MX bike, like the BSA factory engined 500cc works specials. A works bike was not to be had by anyone other than a rider the stature of BSA factory rider and 2 times World 500cc MX Champion Jeff Smith. The only way to ride an English four stroke and have a chance against the growing onslaught of European two strokes was for Alan to build his own special. Just the right opening came at the collapse of the BSA Competition Department, and the selling off of various works frames and other needed parts. Unfortunately, or so it might have been seen by Clews at the time, was that no works engines were to be sold off. Clews saw his opportunity all the same and bought all the works parts that were available for his own use. But, instead of assuring his own supply of works parts, Clews started building MX bikes in his garage. Not having works engines just made Clews develop his own extensive improvements to the standard BSA B50 500cc engine which could be had by breaking up existing BSA B50 MX bikes.
Word got out, if you wanted a BSA 500cc Special that could compete with the likes of the production CZ, Husky, and Maicos of the day Alan Clews was the man to see. He named his first batch of seven bikes Clews Stroka. The first machines also started a design trend that continued to the end of CCM's days, the "scalloped" and lightweighted BSA B50 barrel. The standard BSA barrel was at first machined but later recast by Clews in the classic staggered fin shape. The modification to the BSA B50 barrel was made to lighten the BSA engine but also to keep the English mud from building up during the very wet English scrambles meets. Of course, it also gave the standard BSA barrel a new look that appealed to racers. CCM started out modifying the motor from the very beginning, the first bike built for sale being bored and stroked to over 600 cc. Luck was on CCM's side in 1972 as BSA decided to sell complete but disassembled B50 motors to CCM. No longer was it necessary to find used motors to be fitted into CCM bikes. This was a real breakthrough as BSA had never previously sold engines directly to anyone - not the Rickman Bros. nor Eric Cheney, who were the premier custom frame builders in England.
CCM undertook an extensive development program on the B50 motor resulting in greatly improved power, weight, and reliability. Developed by CCM were the special casting for the barrel, side cases, a four-valve head, improved ignition and lubrication systems and many variations of crankshafts with different weight and stroke length. One of the more controversial modifications made by Clews was mounting the foot pegs directly on the special CCM engines side case to reduce weight and allow for greater ground clearance. Despite reservation by even Clews, the foot peg was shown to fail before the case mounting system did. Even three speed gearboxes were developed to further lighten the bike and strengthen the gearbox by the use of wider gears. Strengthening the gear box was made possible by CCM's wide power band in the 600-cc version. Modification started with the first seven bikes and continued throughout the history of CCM. CCM's motors ranged in size from 500 to over 600 cc with horsepower from 45 to over 50!
Englishman John Banks narrowly missed winning the World Championship twice while on the BSA factory team. CCM thought that when John Banks signed on to race for CCM in 1974 that a world championship could be in their future. But it was not to be. Banks very considerable size and extremely punishing "sit down" riding style caused his CCM race bikes to fail in ways that would be unexpected. This fact was both a problem for CCM and at the same time compelled the factory to further increase development of the works and production bikes. As an example of how tough Banks was on equipment, his first races on CCM ended when the bars broke in half from John's punishment! The factory's intense development resulted in the 1974 1/2 CCM Works G. P. Replica.
The unrestored and barley ridden 1974 1/2 CCM Works G. P. Replica pictured here was very close to the CCM factory machine raced early in 1974. Sometimes referred to as a "John Banks Replica" this model incorporated the latest thinking of the factory. With its short stroke 500 cc motor and a claimed weight of around 220 lbs. this was as good a vintage era English four stroke as ever produced.
CCM never won a world championship but the company upheld the English four-stroke banner nearly to the end of the 1970's. The European two strokes were cheaper, faster and were more reliable but nothing in its day looked so good or sounded as good these booming four stroke MX bikes.
Specifications for CCM 1974 1/2 Works G. P. Replica
- Grande Grix Motor with lightened internals
- Wide power band means that multi-speed gearboxes are unnecessary, motor acts as third brake
- New oil system incorporating full flow paper filter with pressure feed to rockers and cam
- Long movement suspension coupled with hand cut tires gives superb handling in wet or dry conditions
- The lightest/strongest frame in the world - has better welded joints than any other
- Forks have elektron parts for high strength/weight ratio
- Redesigned hubs in elektron alloy are lighter and stronger and are equipped with interchangeable brakes
- Gearbox is selectively assembled for long life
- New type impregnated foam air filter in easy access box
- Light gauge high tensile steel rims are same weight as alloy but four times stronger
- Machine can be ordered to suit rider weight
Engine
- Four stroke single
- Displacement 498cc
- Bore and stroke 88 X 82
- BHP 45
- Comp. ratio 10.3 to 1
Frame
- T45 TIG welded, chrome plated
- Fuel tank Alloy 1.25 gal
- Oil in frame - 5 pints
- Rear dampers - Koni
- Weight 100 kilo
- Wheelbase 57.5 in
- Approximate wheel travel
- Front 8 1/2 inches
- Rear 5 1/2 inches
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