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Velocette Thruxton
The Thruxton Velo was the final development of
Velocette's pushrod single - a machine that in essence dated back to the mid
1930s, but could top I 10 and still sip fuel at an astonishingly low rate
through its massive racing carburettor.
Thruxton is a race track in Hampshire - one of the many wartime airfields that
found a new use during the 1950s. Racing centred on the endurance marathon for
production machines, the 500-miler. The bikes were substantially catalogue
models and
the entries were shared between two riders. Over the years many British stars
shone in the event, including Dave Croxford and Percy Tait. Machines included
the racing Triumph Bonneville, the John Player Norton Commandos - and the
Velocette.
Velocette singles evolved slowly over the years.
Their basic formula was laid down by the 1934 250cc MOV, with the camshaft
mounted high up and the pushrods kept as short as possible, while their narrow
crankcase, slimline clutch and outboard chain run dated back to the early
vintage days. By the late 1950s the machine had evolved into the 350cc Viper and
500cc Venom which went on to set the 24-hour speed record at an average of 100
mph-plus - an enduring record.
In 1964 the high-cam Velo reached its ultimate
development. The performance of the Clubman's
The ultimate sports pushrod engine (right): tuning the Thruxton included a
special head with extra large valves and a down draught inlet port This was
matched to an enormous Amal GP carburettor that required special cut-aways in
the tanks.
Venom at Thruxton led to the makers offering a performance kit that included a
special head with 2in inlet valve and an enormous Amal Grand Prix carburettor,
plus oil and petrol tanks cut away. Although the 1965 500-miler was on an
alternative circuit, the Velocettes dominated the race, with Dave Dixon and Joe
Dunphy .
The model soon found favour with sporting riders,
for it was a la^ genuine tuned roadster and was well able to cope with everyday
use.
Its finest moment came in 1967 the year of the first Isle of Man Production TT.
In the 500 class, Neil Kelly took the race at just under 90mph, as well as the
fastest lap at over 91 mph. Fellow rider Keith Heckles was second.
Only a little more than 1200 Thruxtons were built, although the relative ease of
converting a Venom meant that there were several more replicas constructed by
private owners. In 1969 the ignition system was modified to coil ignition, as
the traditional magneto had been phased out by Lucas. This was effectively the
swan song, for it bowed to commercial pressure in 1971, still a genuine family
firm after 66 years.
Production racer: (left) in 1967 the Thruxton
dominated the inaugural Production TT, taking first, second and fastest lap. It
was capable of more than 11 Omph and had proven endurance, having broken the
24-hour record.
Velocette Venom Thruxton
Years in production: 1965-71 Engine type:
high-camshaft ohv
four-stroke single Capacity: 499cc Bore and stroke: 86 x 86mm Compression ratio:
9.2:1 Power: 4l-47bhp @ 6200rpm Carburettors: Amal GP Tyres (front/rear): 3 x
I9in/ 3'A x I9in Wheelbase: 543Ain Top speed: 110 mph
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