Yamaha TZ750A "Aerofoil"

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One of the most outrageous Yamaha TZ750 racing bikes was built over 30 years ago in New Zealand by Roger Freeth. Read the story and gaze at the fascinating pictures!

 

Rodger Freeth’s Aerofoil Viko TZ750A

By Terry Stevenson.

Terry-San is a very well-known Journalist and Photographer from New Zealand and gets on with equally well-known people as you see!

 

Terry Stevenson and Valentino Rossi
Terry Stevenson and Valentino Rossi

In the mid 1970s, Rodger Freeth needed to find something extra to compete in the upcoming New Zealand Marlboro Series on his aging Yamaha TZ750A (TZ700).

Still a university student, Freeth designed a set of aerofoils to fit onto his TZ750A in late 1977!

The 22 year old effectively created one of New Zealand’s most controversial racing motorcycle experiments. Shortly afterwards, they were banned by the then controlling body, the New Zealand Auto cycle Union (NZACU).

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Freeth, a graduate in Astro Physics, used an early computer to generate the required shapes. The rear wing is 700mm wide and the front pair, hung off the front forks, is 660mm combined width.

The key reason for the aerofoils was to get extra down force on the tyres in mid-turn, to improve cornering speed. A recent track test by the author on the recently reconditioned Trevor Taylor owned bike proved these to cause too much wind drag, robbing the big TZ of vital top speed. Because of where the rear aerofoil was positioned, they also changed the centre of gravity significantly. A bit like having a few bricks placed inside the top of a road bike top-box, hung off the back of the seat.

Freeth first practiced on the aerofoil-shod Yamaha TZ750A at Pukekohe on the same day that Mike Hailwood rode Bob Haldane’s TZ750 OW01 replica, in preparation for Hailwood’s famous 1978 Isle of Man TT comeback. ‘The Flying Doctor’ only raced a few events, mostly with just the front wings fitted, before the NZACU met with Freeth and banned them, the last bike to be banned from NZ competition in such a manner.
At the time, riders were concerned what would happen if other bikes sprouted aerofoils, and they became locked together in a corner!
The publicity generated by the ban created huge industry and media interest, which didn’t hurt Freeth or his Viko sponsor. With some riders unfairly saying it was just a media stunt.

With no instructions, and a poor photo to go off, Taylor incorrectly fitted the rear aerofoil off the back of the rear sub-frame, which Freeth had attached to the rear swingarm via a linear bearing in the seat. Another test with the correct arrangement will follow when the modifications are made.

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The late Rodger Freeth went on to win two Arai 500 endurance races at Bathurst, Australia in the 1980s, plus many NZ titles on NZ-built McIntosh Suzukis incorporating GS1000 and GSX1100 motors, with McIntosh frames.
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