Pete Smith of Epicycle Engineering (later involved with the Australian Ducati Dealer superbike team) owned and rode a 500 Sport Desmo back in the '70s. He then decided to race one but the engineering side of things took over and the actual riding duties were passed on to others. From 1979 until 1985 the bike constantly evolved and proved an excellent marketing tool for Pete's engineering skills. But that is only the first part of the bike's history!
Several notable modifications were done. The crankshaft was replaced by a high chrome steel unit machined from solid by Pete (50 hours work) that provided an extra 10mm stroke over the stock 78/52mm bore/stroke dimensions. It was then balanced, ground & nitrided. An alloy spacer was fitted between the cases and barrels.
Venolia 82mm 11.3:1 forged pistons were fitted after weight reduction, together with conrods made by Pete from 7075TC heat-treated alloy. The end result was a bore/stroke of 82x62mm for a capacity of 720cc. Redline came down from 14,000rpm to a more friendly 12,000rpm. Twin plug heads were done as well increasing the inlet valves from 37mm to 41mm and exhaust from 34mm to cut down 37mm items. Factory racing desmo camshafts (a single model race series was run in Italy, hence the race parts) were also fitted.
The head studs were extended down past the stock level (next to the main bearings) and screw into cylindrical steel nuts. This and the extra support added around the main bearings was done to cure the crankcases cracking. Other features include hinged baffles in the sump to stop oil surge under braking, external oil lines, Kawasaki H2 ignition, heat treated standard gearbox & a dry clutch. cont. cont. An oil cooler from a XJ900 Yamaha was fitted. Also the front calipers are off a GSX Suzuki. The frame was left standard but magnesium Marzocchi forks were fitted along with Pete's mechanical anti-dive system. The first part of the bike's history ended in 1985 after a major blowup at Oran Park after which it sat in Pete's lounge room for 10 years (with some parts finding their way onto his 940cc TL Pantah racer) before the remains were sold to someone who "was after a project".
It was then sold on to a guy who did nothing with it for 18 years before the present owner bought it. However the crankshaft and crankcases had disappeared over the years! Undaunted the new owner had a new crankshaft fabricated by Wes Suffolk and searched for new conrods with the same dimensions - as Pete had told him he had had trouble keeping them straight back in the day. Eventually a pair of Fiat Arbath cr-mo parts were found to do the job.
Another task was to strengthen new cases around the main bearings. Not having access to any photos of the additional welding originally done, a large internal bracing plate was designed & fitted to the left hand case together with a C3 outrigger bearing. The end of the crankshaft was changed to fit a modified PVL brand ignition, designed for a 500 Honda twin set at 32° BTDC. The original 41mm Malossi carbs went on the 940cc Pantah and have been replaced by 40mm Dell'Ortos with the frame scalloped for clearance.
Text and image courtesy Phil Aynsley. .
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