this will sum it up:
Quote:
While it has been years since bugs have emigrated with Ducati's. But the machines still have their quirks. Take the Desmodromic valvetrain-please. On a regular engine, the egg-shaped camshaft lobe turns and pushes down on the valve to open it. As the cam turns back to the fat part of the egg a coiled metal spring wrapped around the valve closes it. It's a simple system and it works, but that hasn't always been the case. After WWII, engine speeds increased beyond the capabilities of the metal used for valve springs. As springs began breaking with greater regularity, the Mercedes Benz race team invested millions in researching Desmodromic actuation. This was (and remains) a Rube Goldbergian system that uses one cam lobe to push the valve down and a second with a rocker arm attached to the valve to lift it up in place of a spring. Mercedes, who somehow rationalized a car with gullwing doors in the same period, ultimately rejected Desmo as too complicated.
Ten years later Ducati adopted it for their motorcycles and it remains on all Ducs to this day. Never mind that years before it debuted Germany and Japan had found a nickel formula for valve springs that allowed astronomical engine speeds without Desmo. Today the system is a handicap on Ducati racing motorcycles. Where comparable bikes can reliably run at beyond 12,500 rpm the Ducati's risk destruction beyond 11,500. That seemingly small difference is largely credited to Honda's advantage that lead to a World Superbike Title in the first year of racing its RC-51 "Duck Hunter".
None of this matters to the Ducati faithful, for them it would be blasphemy to abandon the ass-backwards solution to a problem that hasn't existed for decades-even if it does create a problem now. But remembering my last valve adjustment on a 916 is what burned a hole in my head after I answered the phone. Step one in doing a routine valve adjustment on a 916, 748 or 996 is removing the engine from the motorcycle. This isn't in the shop manual-it is a shortcut mechanics have come up with in the field.
It doesn't get better after that. The clearance between the rocker arms and the valve assembly is set with a removable metal shim that sits in a bucket that covers the valve spring. The shims come in different thicknesses and you replace it with the one that brings the clearances within tolerance. That's a common setup on motorcycle engines today, but only Ducati offers replacement shims in "rough" sizes. To save a couple of lira on having to stock a lot of sizes, Ducati only offers a few and has the mechanic machine them down to the needed thickness. That makes the Ducati you see on this page (and its predecessors) the only motorcycle where you need access to a machine shop to do a tune up. (It is also why the typical bill for servicing a liquid cooled Ducati is north of $300 if the shims need to be replaced.)
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plz note, servicing DOHC Duc's is a lot more expensive then the SOHC Duc's...
I still love em tho, and would own one if I had the cash...
but I wont have that kind of cash anytime soon and I'll be pleased as punch with a new RC51 in spring
