The birth of the L twins

On the early Ducati L motors, a pair of shafts took their drive from the end of the oil pump/ point’s drive which, in turn, got its drive from the end of the crank via 45-degree bevel gears. The rotary motion is sent to the cams via another pair of similarly angled pinions. Truth be told, every time rotary motion is twisted by 90 degrees there’s a reduction in power; hypoids absorb up to 12%, bevels variously 3-5%. Taglioni was happy to lose this level of power because the trade-offs were actually beneficial. The relatively small losses in power at the bevels was comfortably offset by the increased precision in cam timing and, crucially for the racing machinery, allowed Desmodromic valve gear to work at its very best. The one thing bevel valve gear isn’t is cheap; from crank to cams there are nine bevel gears, each with some form of bearings and relevant shimming. This costs serious money to produce and install. The move to belt drives for the cams came with the advent of the Ducati Pantah in 1979. Cheaper to produce and fit, quieter in operation and more reliable, it was ultimately a no-brainer for Taglioni, who had dallied with the set-up in the early Seventies. By 1979 internally toothed cam-belts were finally up to the task in hand on motorcycles. Initially pioneered in the car world from the mid-sixties, manufacturing technology had at last caught up with market requirements and rubber belts activating poppet valves was common place. Fitted to the Pantah’s engines, the blueprint for every modern Ducati had been laid down.