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Fruin were motorcycles produced from 1957 to 1963.  Having already been a keen supporter of 125cc road racing during the 1950s, we move towards the end of the decade when Bert Fruin became interested in the new 50cc racing class. He then went into limited production of machines for that class, plus a similar one for sports road use. Both machines used the Italian DEMM engine, and tubular frames with conventional suspension. The motorcycles were sold as the "Dartela". Bert rode one of his machines in the 1962 50cc TT race.        He later built a 125cc twin engined DOHC motorcycle and was a regular contender in UK racing events, as well as four further TT races.
H. L. (Bert) Fruin   The Fruin Dartela
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The Fruin Dartela, with Bert Fruin at the 1960 50cc Enduro held at the 
Snetterton Circuit in Norfolk 
The Rider is R.G.Harris (George) and his co-rider was Jock Wright
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Bert Fruin at Silverstone 1958 
The Fruin Dartela at Silverstone 1958
The Dartela 50cc Racer
The ex-Bert Fruin, 1962 Isle of Man TT - Fruin Dartela 50cc Six-Speed Racing Motorcycle Engine no. 31663

The 50cc racing motorcycle pictured in the gallery below, is the work of independent engineer H L 'Bert' Fruin of Hillingdon, Middlesex, who constructed a series of technically interesting 'specials' in the 1950s and 1960s, including a DOHC 125cc twin-cylinder racer and a modular V4/V8 engine.

Proprietor of H L Fruin Motorcycles in Hillingdon, Bert began competing on his Italian DEMM Demon-based 50cc two-stroke Dartela racers in the late 1950s and rode them at the Isle of Man TT in 1962 and 1963, retiring on both occasions. (He also built a 200cc Four using Demm top-ends and later NSU Quickly components, which was sold in kit form as a crankcase and set of crankshaft blueprints).

Further tuned by Bert, the 50cc Demon engine went into a frame of his own design. Although it fared reasonably well against the ubiquitous ITOMs, the Dartela was handicapped by its three-speed gearbox (the ITOMs had four speeds) so for the inaugural 50cc Isle of Man TT in 1962, Bert produced a longer frame to accommodate an additional Albion two-speed 'overdrive' gearbox (actually a horticultural cultivator box, suitably modified) giving six speeds in total.

The integral gearbox was operated by a twist-grip on the left handlebar, the overdrive by a foot change on the right. Ridden by Bill Fruin himself, the solitary six-speed Dartela retired with engine trouble on the first lap of the 50cc TT, a race won by Suzuki-mounted Ernst Degner. Bert recorded another 'DNF' at the 1963 TT but it is not known whether he rode the six-speed Dartela on that occasion.
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Just two examples of the 200cc, four cylinder, two-strokes were produced by Bert  in 1961. The Fruin bikes were originally sold in kit form but this was short-lived due to the complexity of is design and high cost. With hindsight its not hard to see why. The engine was sold as un-machined castings and the four coil, four breaker electrical system was crude. This restored bike is, though, nothing short of a masterpiece.
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The bike below is the 1965 Fruin 200cc Four-cylinder Racing Motorcycle Frame no. 419220S Engine no. BF2. The engine of this extraordinary motorcycle is the work of independent engineer H L 'Bert' Fruin of Hillingdon, Middlesex, who constructed a series of technically interesting 'specials' in the 1950s and 1960s, including a DOHC 125cc twin-cylinder racer and a modular V4/V8 engine. Proprietor of H L Fruin Motorcycles in Hillingdon, Bert began competing on his Italian Demm-based 50cc two-stroke Dartela racers in the late 1950s and rode them at the Isle of Man TT in 1962 and 1963, retiring on both occasions. The first Fruin-built 200cc Four was featured in The Motor Cycle magazine (3rd May 1962 file), which also revealed his plans for future multi-cylinder 'strokers'.
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Designed to accommodate Demm top-ends and later NSU Quickly components, Bert's four-cylinder engine was sold in kit form as a crankcase and set of crankshaft blueprints at a cost in 1961 of £16. The engine of the machine shown here was built by engineer Mike Smith of Waltham Abbey, Essex around 1965 and uses NSU cylinders and heads. It was fitted with Wal Philips fuel injectors initially and then Dell'Orto carburettors. Mike Smith housed the Fruin engine in an MV Agusta rolling chassis fitted with Royal Enfield forks and Gilera hubs. Power reached the ground via a Villiers four-speed close-ratio gearbox. Motor Cycling magazine featured Smith's Fruin Four in its 24th July 1965 edition. The Fruin proved un-competitive in 250 classes so Smith used it mainly for sprinting.
At some time in the 1980s Mike Smith sold the Fruin to Kevin Burton, who in turn passed it on to Tony Milk of New Costessey, Norfolk. In 1999 Mark Turner of Track & Classics, Stockport bought the bike from Tony Milk who had advertised it for sale in Old Bike Mart. It is understood that the Fruin was run but never raced by Tony Milk. Mark Turner made a new fuel tank and re-commissioned the Fruin, which was run at his shop in Stockport and again at a classic motorcycle event at Elvington Air Museum. While in Mark Turner's ownership the Fruin was the subject of an article in Classic Bike Guide (March 2000 edition).
Turner then sold the Fruin to a collector, from whom it was purchased by the current owner and restored by Noisy Toys in 2009. Refurbishment included rebuilding the engine and gearbox, repainting the frame and fuel tank, re-plating the brightwork, overhauling the carburettors and float bowls, and rebuilding the wheels. The electrics remain original and un-restored. Following its restoration the Fruin was displayed on the Carole Nash stand at the NEC, Birmingham and also at the Stafford Show.
Research:
JEEP's Archives
IoM TT information pages
Motorcycle Magazines
Bonhams - Auctions
On-Line encyclopedias
News Paper Cuttings
Scrap Books/ Submissions
I am always looking for contributions to the web page. Please let the web master know if you have any information or pictures for them. If I have used a picture that requires permission please contact me.
C.1903 WYATT-MINERVA 331CC MOTOCYCLETTE - Registrationno. H 338 Frame no. 8133 Engine no. 9244
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Well before the racing bikes Bert owned a truly Vintage machine. I include it here to show his previous interest in motorcycles.  My thanks to Bonhams for this information.
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• Previously owned by H L'Bert' Fruin
• Present family ownership since 1953
• Pioneer Certificate
Although a late comer to bicycle manufacturer, the Belgian Minerva concern was among the first to offer a viable proprietary engine for motorcycles. Nominally of one horsepower, the 211cc unit was designed for attachment ahead of the cycle's front down-tube - a location which became known as the 'Minerva position'
This Minerva-engined machine is badged as a 'Wyatt Minerva', though whether 'Wyatt' refers to the make of bicycle or the shop that assembled the machine is not known. Driving directly by belt, the engine displaces 331cc and has the 'atmospheric' type of inlet valve and a mechanical exhaust valve.  An older restoration of 'H 338' states that this was previously registered to independent engineer H L 'Bert' Fruin of Hillingdon, Middlesex, constructor of a series of technically interesting 'specials' in the 1950s and 1960s, including a DOHC 125cc twin-cylinder racer and a modular V4/V8 engine. Bert Fruin rode the Wyatt-Minerva on the Pioneer Run at least once, and sold it to Stan Gilks in February 1953 (see documentation on file). The machine was last taxed in April 1966.
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