Cagiva’s TDR that never was
One-off special recreates legendary designer Tamburini’s supermoto dream
Legend has it that Massimo Tamburini sketched this 100bhp supermoto – complete with Bimota V Due engine – while working for Cagiva, but the design never left his drawing board. Twenty-odd years later, British engineer and Cagiva fanatic Gavin Robertson has managed to finish the maestro’s work.
The bike is a phenomenal effort, taking a few clues about what Ducati 916-designer Tamburini intended and turning them into a fully functioning machine powered by Bimota’s ill-fated but frisky two-stroke twin. ‘I was doing some business with Bimota,’ Gavin tells Bike, ‘and heard a rumour that years ago the chief engineer – Marconi – had sent a V Due engine to Tamburini [who used to be Marconi’s mentor before moving to Cagiva].
‘It’s alleged that Tamburini had penned an outsized Super City [Cagiva’s 1992 125cc supermoto] using the Bimota engine. But Bimota weren’t healthy enough to supply the engines and nothing was ever done. Apparently later, when Cagiva were about to do it, Bimota went bust.’
Fired up by the story, 61-year-old Gavin sprang into action. He bought a Super City and drew a longer, wider, taller version to fit around the V Due engine. ‘I designed a frame in the same way Cagiva would build their race frames back in the day. They used to put a big boss on every tube to get a larger working surface area for the weld, so we did that. ‘The frame builder I use is a guy who builds speedway and grasstrack frames, and this was his first road bike. We took a V Due frame and jigged it, then we stretched the jig and fashioned something we knew would fit the engine.’
V Due engines are notoriously fickle, particularly when running Bimota’s direct injection system, so Gavin used carbs instead and sent the motor to a Bimota specialist in Germany. ‘He re-engineered it and set it up – it made 97bhp, because I didn’t want it too peaky. The really good ones with carbs run at 99-101bhp. Then it went to Belgium for a friend to build the rear suspension.
‘We tried different mechanisms for the linkages, using Cagiva rising rate set-ups with the rockers.
The long strut [which moves the shock out of the way of the exhaust] was originally used in the
Cagiva GP bikes.’
The exhaust was made by
Tony Green, who used to make exhausts for Ron Haslam back in the day. Tony used the
Bimota exhaust for his calculations and then fashioned a complete new set of pipes to go through the frame. ‘The whole project took about two and half years, but a lot of that was waiting for people like Tony to do their thing. But I was fine with that – I was infatuated with a girl when I was 14 and didn’t talk to her until I was 16, so I don’t mind waiting.’
‘There’s a lot of interesting engineering in this bike. For example, the water pump is an electric one from a rally car, so if the engine’s cold, the waterpump only revolves at 5rpm, and as the engine gets hotter, the speed increases so you don’t need a thermostat. It means you can run at maximum revs without overheating because the pump is doing 16,000rpm.
‘My plan for the bike is to do a hillclimb in France and scare myself senseless, then I might sell it. I’m not precious
– and I’d like to build another one using a Tesi chassis. I was offered £30,000 for it, which sounds about right, though once it’s upside down in a ditch in France it’ll probably be worth about £8000.’