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A BRITISH RACING 50
IN KIT FORM
This article was taken from a scrap book, created by Dave Brearley, an avid supporter of the Racing 50cc Scene. The quality of the print was bad and there were no dates or attributes attached and so I have reproduced it and accept that it might infringe copyright.  If so will the writer please contact me for permission to be granted. I have also added some more information not available in the article and links to other relavent pages.
A CHANCE telephone call led me to a back street in the peaceful Hertfordshire town of Stevenage, and to the inconspicuous shop beneath which a blow is being struck for the British motorcycle industry.
It is here that work has been going on since last October on the designing and manufacture of Britain’s ?rst production racing 50 cc machines. I say machines advisedly because there will be three types of machines available; an ohv model along with single and twin-cylinder two-stroke models.
The twin-plug two-stroke engine unit in close-up (above) and in situ (below). The down-draught Amal carburettor, the twin coils, and the stylish shaped hump-back tank can be clearly seen. Note, too, the fibre-glass moulded seat and the ultra-lightweight aluminium mudguard.
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The men behind this bold adventure are a rare combination - a Scot. Duncan Mitchell, and an Irishman, Shaun Mooney both with national brogues you could cut with a knife. Unusual too in that both are tee-total and only Duncan smokes. Duncan is in charge of design while Shaun looks after the technical side of things.
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I asked Duncan what led them to enter this field in competition with the already established imports from Italy and Japan. He told me: “We have both raced 50s for quite some time since I guess at Blandford in 1956 – and after experimenting with various machines available, felt that we ought to put our own ideas into Practice”. I asked them was it easy? Shaun told me: “We approached many British component manufacturers and asked If they would supply us with specialised items. “Many did not even answer, a few answered and said they were too busy to disrupt production for what would only be a small item, while others took the trouble to come round and see us. We have naturally favoured their parts.
We could not find anyone to produce an engine of our design for us, the castings being the problem, so we had to go to Italy for this, as we did the brake hubs”.
I looked at the ohv machine first, which you can see below, the ?rst on the assembly bench. It looks quite functional. It has a duplex frame with single leg telescopic forks, but an optional extra will be an Earles-type leading link pattern. The 18 inch wheels have Avon WMO x 18 racing rims around the 5-inch full width di-cast alloy Forni brake hubs and are fitted with Avon 2.00 inch and 2.25 inch tyres.
The ¾-inch, 14 gauge duplex frame has a rear swinging arm controlled by Girling units, as are the Earles type forks and the three-gallon TT tank is a fibreglass styling made especially for them and has a single centre bolt fitting and a Monza quick-filler cap. Clip-on bars are fitted with a rev. counter and steering damper unit and Doherty control levers.
The engine has a clean appearance, being of unit construction. The cylinder inclines forward at 10 degrees and has the push rods enclosed in the finning. Barrel and head are alloy, fitted with a liner, with a bore of 40mm and a stroke of 39mm, giving a capacity of 49 cc. Operating on a compression ratio of 10:1, it develops 4.2 bhp at 7,200 rpm, although it is envisaged that this will be improved upon after tests and development with lightened fly wheels.
A Battery fed (Varley 3 in 5) ignition is used to supply current to the 14mm plug. The two valves are inclined at eighty degrees and have single coil spring operation. A 15UA Dell’Orto carburettor is fitted, though Duncan said he would like an Amal 274 type to fit on to the tuned induction.
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Refinements A 3-speed foot-change gearbox is fitted at present but they are now looking for some-one to cut their own pattern 4-speed close ratio cluster that fits into the existing shell. A multi-plate clutch operates in oil. The engine has a sump lubrication system. The unit is the ?rst of a batch made expressly for them by Daldi and Matteucci and has needle caged roller main bearings.
Further refinements such as the extensive use of Allan-cap screws and the snail-cam chain adjustment show the thought that has gone into the design,which includes a fibre-glass padded racing seat moulded by Nickri of Goodmayes Essex, who also were responsible for the neat Dolphin fairing with which every machine will be sold. Aluminium guards are fitted front and rear, made by Speedwell,
The overall weight is under 85lbs, and the cost. in kit form is anticipated to be about £160 complete-ready to race. Finish is in black -“Traditional Stevenage colours” said Duncan. Two hours should suffice to construct the machine from the kit parts with the complete tool kit supplied.
The two-stroke engine unit has a Mitchell designed two-plug head, with the plugs inclined at fifty degrees. A specially ported flat-headed piston is used, giving a compression ratio of 17:1 and 7.5 bhp at 9.000 rpm. An Amal GP2 down draught carburettor with rubber mounted remote afloat is used, other specifications are similar to the ohv model the price being £150 complete in kit form.
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The inclined barrels are separate, united Scott-style by a double-sprocket gear to the 5-speed gearbox with dry clutch. Again the other features remain the same as the other models. The price of this is anticipated to be around £200.
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Under a bench I spotted a 50 cc four-cylinder two-stroke engine that the boys have been experimenting but put aside for the moment to await further development. This unit sits across the frame MV style.
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Wheelbase for all models is 45ins, saddle height 25ins, and overall height 32ins. The boys are still looking for someone who is prepared to bend the pipes and fashion the megaphone exhaust systems.
Moto-X next?  They are contemplating producing a Moto-Cross machine before the end of season depending how production of these interesting 50 cc racers progresses,
Duncan and Shaun, with two “sleeping partner” directors, aim to provide ready-to-race 50 cc machines at a reasonable price for the enthusiast, who, like themselves, has found he needs to improve the out-dated imports available at similar cost.
Their product is neat, work-manlike and certainly functional looking. With the tremendous interest in this class this year, they could well strike the jack-pot, I hope they do.
ABOVE: A fine three-quarter view of the un-faired ohv machine. The duplex cradle frame with the single leg teledraulic front fork and swinging rear arm suspension unit can be seen to advantage, as can the three gallon fibre-glass fuel tank. It is anticipated that a lighter Girling rear suspension unit will eventually be fitted.
ABOVE: Inclined toward the camera, the interesting separate-unit twin cylinder engine is still undergoing development. The gearbox cluster units can be seen on the left, with one of the twin carburettor intake units on the right.
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Designer Duncan Mitchell, left, and development engineer Shaun Mooney are shown here at work on the ohv engine unit. This is the engine which is made especially for Moto-Decla, the name by which these 50 cc machines will be known.
(Editors note) The base of this engine was the Fitz Hugh 4 and is covered in a separate page on this site. Please click here to read the story.
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Manufacture | Britain’s | Production | Racing | 50cc | Machines
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