Ducati 350 Mark 3 Desmo

Desmodromic valve actuation came to the street in 1967 with the Ducati 350 Mark 3 Desmo.

Ducati Desmo

Only the ā€œDā€ on the side cover gives a clue to what resides within this second year Ducati Desmo.

Photo By Jeff Barger

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1969 Ducati Mark 3 Desmo
Claimed power:
22hp @ 7,500rpm
Top speed: 112mph (with megaphone)
Engine: 340cc OHC, desmodromic drive, air-cooled single, 76mm x 75mm bore and stroke, 10:1 compression ratio
Weight (dry): 282lb (128kg)
Fuel capacity/MPG: 4gal (15ltr)
Price then/now: $839/$4,500-$8,000

It’s a long transition from a Doodlebug scooter to a 1969 Ducati 350 Mark 3 Desmo. In fact, it would be difficult to find a better example of two-wheeled evolution — from antiquated to advanced.  

In the early 1950s, Don Smith rode a Doodlebug scooter with a Briggs & Stratton 1-1/2 horsepower engine and diminutive tires. His Doodlebug was direct drive, missing the fluid clutch it would have had when delivered new from the Beam Manufacturing Co. of Webster City, Iowa. At stop signs and red lights he would lift the rear wheel, then, with the intersection clear, he’d drop the back of the scooter and open the throttle. Don wasn’t going anywhere fast.

He was just 13, and the Doodlebug scooter, his first ride, was freedom. Don’s never been without a motorcycle since. Over the years he’s owned different makes including Harley-Davidson, Honda, Moto Guzzi and Triumph, but he has a soft spot for Italian products.

A retired ironworker, Don worked building bridges and towers in his home state of Wisconsin. Some 13 years ago, he turned his attention to motorcycle restoration. “My son, Scott, found a 1966 Ducati Monza Jr. 160 and said he’d like to restore it,” Don says. “But he didn’t have time and I’d just retired, so I took over the job — that was my introduction to complete restorations.”

Don’s motorcycling history is quite interesting. His first “big” bike was a Harley-Davidson K model. But his friends were all riding British, so he bought a brand new 1960 Triumph TR6, which he then traded in 1965 for a Bonneville. When he heard about the Honda CB750 Four in 1969 his name was second on the list at the local dealer. He bought another CB750 in 1971, followed by two Suzuki GT750s — one 1972 and the other a 1973 — before buying a Kawasaki 900 in 1974.

“The Kawasaki went fast in a straight line, but it wiggled around the corners,” Don recalls. “I preferred handling over straight-line speed, so in 1975 I got a Moto Guzzi 850T, and then traded that in 1977 for a Moto Guzzi LeMans. I didn’t think anybody could build anything better than that, and I still have that bike.”

Every two or three years, he’d buy or trade up, and if he had any emotional attachment to a motorcycle, he’d keep it — witness the LeMans and his 1992 900SS Ducati, which now shows 55,000 miles on the clock. There are currently 18 machines in his collection, and one of them is this 1969 Ducati 350 Mark 3 Desmo.

Taglioni’s designs 

The Mark 3 D is about as far from a Doodlebug as one can get, and the difference in technology is thanks to Italian designer Fabio Taglioni. In 1949, Taglioni sketched a 75cc double overhead cam engine as a design exercise while studying for his doctorate at the University of Bologna. He sold the resulting engine plans to Ceccato, and then studied for two years under Alfonso Drusiani at Italian motorcycle manufacturer Mondial. Taglioni joined Ducati in 1954, and his first design was the 98cc bevel gear overhead cam Gran Sport, which was nicknamed “Marianna” in Italy.

Taglioni’s Gran Sport proved competitive in Italian race events during the mid-1950s, sweeping its class at the Milano-Taranto and the Giro d’Italia races. Grand Prix racing was next, and Taglioni’s design brief netted a 125cc double overhead cam single. Although reliable, the engine wouldn’t rev high enough to make decent power. Allowed to rev out at 11,500rpm, the valves would float and hit the piston crown. Looking for a solution, Taglioni settled on desmodromic valve actuation.

Overhead valve engines use a cam or pushrod and rocker to open the valve but rely on spring pressure to force the valve closed. Desmodromic engines instead use separate rockers — one to push the valves open and another to pull them shut. This helps avoid problems such as valve float and valve spring failure. Taglioni did not invent the desmodromic valve concept, and the technology has been around since the early years of the 20th century. Other motorcycle engine designers tinkered with the approach, including Norton and J.A. Prestwich. In the mid-1950s, automobile manufacturer Mercedes-Benz famously and successfully campaigned desmodromic valve engines in the W196 racer.

Desmo debut 

With desmo actuation, Taglioni’s single could cleanly rev to 12,500rpm, and in 1956 the 125cc works racer took the win in its debut at the Swedish GP.

Although the desmo was successful at the track, Ducati’s road-going singles used bevel drive overhead camshafts and rockers, with enclosed hairpin valve springs. This engine style became widely known as the “narrow case” design, with front and rear engine mounts the same width. Ducati singles grew from 100cc to 125, 160, 200, 250 and 350cc models, and of them all, the most memorable would be the 250 Mach 1.

In 1967, Ducati launched a redesigned frame featuring twin tubes running from the back of the gas tank down to the swingarm pivot. This new frame required a wider rear engine case mount — approximately 3 inches wider than the front — and these subsequently became known as “wide case” engines. Between the two styles, narrow and wide case, the basic architecture remained the same.

Ducati brought the new frame and wide case engine design to the street in 1968, first in the street-legal 350cc Scrambler, then also in 250cc and 450cc models. All of these used a bevel drive overhead cam with valve springs. During 1968, Ducati finally brought a desmo to the street with the launch of the 250 and 350 Mark 3 D — “D” for Desmo.

The 1968 Ducati 350 Mark 3 Desmo featured a red frame, a red and chrome gas tank with twin-filler caps, chrome fenders, steel rims, a high-lift cam and a tachometer. In 1969, the 250 and 350 were joined by a 450 Mark 3 Desmo, and they were outfitted with a black frame and a single-cap fuel tank and chrome fenders. Non-desmo Ducatis feature a dull silver paint in place of the chrome.

Ducati’s 350cc single-cylinder desmo engine is all alloy with polished cases and massive finning on the barrel, which features a cast iron liner. Bore and stroke are 76mm by 75mm for a capacity of 340cc, with a 10:1 compression ratio. The 5-speed unit construction gearbox has a heel/toe shifter on the right side of the engine, with the kickstarter on the left.

Cycle magazine tested the Mark 3 D Ducatis, including the 250, 350 and 450 models, which, apart from engine size, are of the same overall dimensions. “The Ducati’s single-cylinder engine has narrow cases; therefore, the frame, the tank and the footpegs can all be very narrow, too. You can fit yourself more easily to a well-laid-out narrow motorcycle than you can to the fat bikes, and the result is a feeling of instant confidence … the Ducatis feel as though they had been built just for you, and that they weren’t something that came out of a crate,” Cycle said.

Of the 350cc desmo engine, they wrote: “The 350 was more highly tuned and had a narrower powerband; the power came in at about 6,500rpm. The 350 is tuned as a street dragster; the 250 and the 450 are over-the-road bikes.”

Don’s 350 D 

Don found his 1969 350 D at the 2010 Barber Vintage Festival swap meet in Birmingham, Ala. He and a friend had driven to the event, as he had no plans to purchase a motorcycle. Luckily, friend Erik Eskildsen was driving through to Florida with his truck. He told Don if he found something he couldn’t live without he would haul it south with him, and bring it home to Wisconsin in the spring.

Don was drawn to a Benelli being sold by father and son team Dwight and (the late) Brian Corley. The Benelli was already spoken for, but then he noticed a Ducati single-cylinder engine.

“The head had been removed,” Don says. “Dwight told me the desmo head was good, but the engine was seized.” Dwight picks up the story. “My son and I were mostly into British bikes, but we heard about this Ducati in Georgia, so we went to have a look at it — it had seen years of exposure, but we picked it up thinking we might be able to redo it. The more we looked at it the more we thought somebody else could probably do something better with it.”

The rest of the bike was stored in the Corleys’ trailer behind their camper. “The bike was a wreck,” Don explains. “The wheels were frozen and badly rusted, the alloy hubs were crusty and the entire bike was rusty. There was a dented Ducati Scrambler tank and a high handlebar on it.” However, because it had a Desmo engine, Don paid the Corleys $1,500 and had Erik haul it home to Appleton, Wis., by way of Florida. Don didn’t get to work on the bike until the spring of 2011. Stripping the Ducati down proved the frame was straight, but the swingarm pivot bolt was rusted in place. Don drilled small holes in the back of the swingarm and filled the cavity with penetrating oil. “I had a punch the exact size of the shaft, and every so often I’d give it a crack. After two months, it finally moved,” Don says.

With help from Jonathan White of Prova LLC in Cincinnati, Don began accumulating the correct pieces for his 350 D, including a coffin-style tank and the correct steel front fender, both sourced on eBay. The fenders, springs, kickstarter and shift lever were chrome-plated. The frame was powder-coated black, and Bryan Gagnon of B&J Custom Cycles & Graphics in Shawano, Wis., finished the gas tank and side panels cherry red, a hue Don says is slightly darker than what Ducati would have used. The bike was missing its seat, so he found a used seat pan and had a new cover stitched by Korth Upholstery in Appleton. Don polished the alloy wheel hubs and laced them to 18-inch stainless steel rims with stainless spokes. As for the engine, Don says he couldn’t have completed the build without help from friend Erik King. The lower end proved to be in fine fettle, but while it was apart everything was polished, and the crankshaft was treated to new bearings. A used muffler and header pipe came from eBay, and both were chrome-plated after Don removed the muffler baffle. On the 1969 350 D the correct carburetor is a Dell’Orto SS1 29D, and Don’s machine is so equipped. Chris Dietz of Motion Products in Neenah, Wis., rebuilt the Ducati wiring harness, Don detailed the hand controls and levers, and new rubbers and cables completed the build.

The finished product 

“It was scary to fire it up for the first time,” Don says. “You’ve got to kick it deliberately, because it’s got great compression and will kick back. They’re all a bit different to start, and I haven’t got this one down quite yet, but it did start on the fourth kick and it’s been running good since. You can just about feel the piston going up and down when the bike takes you forward, and it handles great. You can carry a lot of speed into a corner because it’s so light, and that really makes it fun to ride. The brakes are a bit weak, but because the bike is light they’re really not a big issue.”

Don restored his Ducati using original components, and with the materials that were available when the machine left the factory, as much as possible. “I want to transport myself back to that time, and I restore them so I can appreciate what I used to ride,” Don explains, adding, “I restore them to preserve an old bike, not to make an old bike modern.” MC