The History And Mystery Of Ducati’s Desmodromic Valves 

Summary

• An old but advanced technology, desmodromic valves helped engines rev higher when springs failed.
• While Ducati sticks with tradition, modern engines are moving away from desmodromic valves for reliability.

The dreaded Desmo service is what Ducati motorcycles are infamous for. A single service can cost you nearly a thousand bucks, and it creeps out on you quickly if you ride regularly. That’s sure to send shivers down your spine. Talk about being expensive enough to make many prospective buyers exit the Ducati showroom and enter a Japanese one. And we don’t blame bikers on forums who say, “If it’s a Desmo Duc, you’re the test rider.”

Still, a case has to be made for the alluring desmodromic valves that Ducati bikes are known for. This system was once an engineering marvel that helped motorcycles and cars win races — even Formula 1 — but it has fallen out of fashion today. It’s a niche tech that only a certain Italian motorcycle manufacturer uses as a homage to tradition. Does it need to? Nope. Does it, anyway? Yep. So let’s dive into the history of desmodromic valves and what they mean for automobiles.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from Ducati and other authoritative sources, including Desmodromology and Motorcyclist Magazine.

Ducati Wasn’t The First Desmo User

It’s 2024, and Ducati is synonymous with desmodromic valves, but surprisingly, this Italian company wasn’t the first to use them. Desmodromic valves date back to 1889 when Daimler-Benz patented the tech for its V-twin car. It wasn’t until the 50s that desmodromic valves became popular, with more motor companies jumping on the desmo wagon. Even Norton had a go at it, but the most notable implementation (at least for cars) was the 300SLR, also known as Uhlenhat coupes.

In the same decade, Ducati joined in. The manufacturer was suffering, and Giuseppe Montano (General Manager) thought “racing on Sunday, selling on Monday” could favor the brand. So, he tasked the young, talented Fabio Taglioni with the task. Taglioni implemented the design in the 1955 Ducati 125, which allowed the company to win many races. Even today, most Ducati motorcycles, including the Desmosedici GP24 MotoGP motorcycle, use desmodromic valves. Over time, other manufacturers moved to spring valves, but Ducati stuck to the tradition.

Notable Implementations Of Desmo Valves Other Than Ducati

• Pomeroy Grand Prix Car
• Azzariti’s 173cc and 348cc engines
• Mercedes-Benz W196 Formula One
• Mercedes-Benz 300SLR
• Fiat T.801
• Maserati 372 DS
• Norton Manx 350 & 500
• Moto Morini 250 GP

Desmodromic Drama In The Engine Heads

An internal combustion engine uses valves to allow the fuel/air mixture and exhaust fumes to enter and exit. As the piston goes up and down, these valves need to open and shut at precise times — it’s a well-choreographed mechanical dance. These valves are perfectly timed to the crankshaft, and a system connects the two. As the crank spools up, the system spins the camshaft (in the head) with lobes that actuate the valves. In most engines, the cam acts on the rocker arm or a shim bucket to open the valves.

Where desmodromic valves differ is how the valves are closed. In a regular system, the valves are pushed shut with springs. On the other hand, desmo heads have a separate cam paired with forked, L-shaped rocker arms that close the valves. In simple words, a regular head uses rocker arms to open the valve and lets the spring close it. But a desmo head uses two rocker arms to open and close the valves — perfect timing.

When Metallurgy Wasn’t Perfect, Engines Barfed Out Valves

Why were desmodromic valves so popular back then? One simple reason: they allowed the engines to rev higher. Back in the day, metallurgy wasn’t perfect, and springs weren’t fancy or reliable. When you revved the engines higher and higher, the camshafts turned faster and faster — so fast that the springs couldn’t keep up. The valves would open and stay open as the springs failed to return the valve shut. Enter, valve float.

If you know anything about engines, you’d know mistiming is sinister for engines. Once the valves start floating, it’s only a matter of time before the piston makes contact with the valves and everything turns to salad in the cylinder. It begins with a ticking noise but soon turns into broken valves, a seized engine, and an expensive repair bill.

Back in the 50s, you had two options: either, let your engine produce gallops of torque at low revs and avoid the high revs, or implement desmo valves to help the engine rev higher. The springs simply couldn’t keep up with high revs, so the desmo valves came in handy as they forced the valves to close every time. Problem solved.

Dreaded Desmo Service That Need Not Be (And May Not Be)

The word desmodromic scares people, but you don’t need to be. Yes, servicing Desmo engines is expensive, but at Ducati, not when you do it at home. We’re not kidding. If you can service spring valves, you can service desmo valves, too. It’s the same process but only the valves are twice as many. So, yes, it will take a lot of time, but it’s nothing specifically different. Servicing Desmo is as complicated as spring valves.

Still, there’s no denying that desmodromic valves are now obsolete. Think of the Yamaha R6, a screamer that can rev up to 16,000 RPM — it never used desmodromic valves. It didn’t need to. Metallurgy has come a long way since the 50s, and springs can now keep up with insanely fast-turning cams. There’s a reason your mechanic will probably laugh at you if you ask them to check the valve timing on your one-year-old Japanese crotch rocket unless there’s something wrong with the engine.

Still, Ducati uses them. Modern liquid-cooled Ducati engines even have service intervals on par with Japanese manufacturers. Thanks to synthetic oils, new-tech Kevlar cam belts, and lighter reciprocating parts, these have pushed the valve service interval upwards of 15,000 miles. Ducati has even moved away from the desmodromic valves with the Multistrada V4 with the Granturismo V4 engine, setting tradition aside for reliability and longer service intervals. How long? A whopping 36,000 miles of major service intervals. That’s a long, long time.

Notable Ducati Engines With Desmodromic Valves

• Superquadro Mono
• Desmodue
• Testastretta 11°
• Desmoquattro
• Superquadro
• Desmosedici Stradale

Honestly, it’s sad to see another awesome technology being replaced with something else, but that’s how it is. New and improved features will always replace older tech, regardless of how charming or cool they are. Yes, we will miss the desmodromic valves — they have a certain charm to them, although most riders can never tell what kind of valves their bikes are running unless the spec sheet mentions it.

As Desmo valves become relics of automotive history, their eventual disappearance makes one wonder. In a world where innovation reigns supreme and cherished traditions are cast aside in pursuit of progress, what other brilliant automotive technologies will be swept away by the tide of change? Does anything come to mind? Tell us in the comments!