Ducati 250, 350 and 450 Mark 3 and Desmo servicing
1968 to 1974 · 239cc to 436cc bevel-drive single, valve springs or Desmo · Greenwich, London
Ray Petty Meccanica services, repairs and restores the wide-case Ducati 250, 350 and 450 Mark 3, Mark 3D and Desmo singles (1968 to 1974) at its independent Ducati workshop in Greenwich, London. Whether your single closes its valves with hairpin springs or with Desmo rockers, RPM sets it up properly and can track down the parts these old engines tend to need.
About the Mark 3 and Desmo singles
Ducati's wide-case engine arrived in 1968, derived from the 250 and 350 SCD racers, with wider rear engine mountings, bigger main bearings and big end, a larger sump and an improved kickstart. It powered the 250 (249cc) and 350 (340cc) Mark 3 roadsters, joined in 1969 by the 450 (436cc, 86 x 75mm), the largest size the engine could reach without a redesign. Each was offered as a Mark 3 with valve springs or a Mark 3D with a Desmodromic head. From 1971 the Desmos became café racers, the fibreglass-tanked silver metalflake bikes nicknamed the Silver Shotgun, then were restyled by Leopoldo Tartarini in 750 Sport colours for 1973. A 239cc version went to France in 1974, the year the factory stopped building overhead-cam singles.
Servicing your Mark 3 or Desmo single
The Mark 3 closes its valves with hairpin springs (the 239 uses coil springs). The Desmo head has a single camshaft carrying both opening and closing lobes, plus light hairsprings kept to help starting and low-speed running, so its opening and closing clearances both need checking. Below the head, Desmo and spring engines are the same: wet sump, gear primary drive, a wet multiplate clutch and one Dell'Orto carburettor, a 29mm square-slide VHB on the 450. Starting is by kick, with a decompressor on the spring-valve engines, and later bikes left the factory with electronic ignition rather than contact breaker points. RPM recommissions singles that have stood for years, working through each bike from one end to the other and calling you before anything extra.
Book your 250, 350 and 450 Mark 3 and Desmo in
Tell us what it needs, or how long it's been off the road, and we'll take it from there.
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Saturday: 10am to 5pm
Sunday and Monday: closed