Evolution of the Moto Guzzi V9’s Engine

Decades of refinement have created this wonderful V-twin.

Moto Guzzi V9 engine static 3/4 view
Moto Guzzi V9 engine.Bruno dePrato

Now that Moto Guzzi's small block V-Twin has come to full maturity—with its final growth to the 850ccs of the latest V9—it's worth retracing the history of this controversial engine.

This engine was requested by the late Alejandro De Tomaso, after the failure of the Benelli 254 and the rather skimpy life of the Moto Guzzi 350 Four, and Benelli 504. It was around 1975 when Mr. De Tomaso put the De Tomaso Automobili technical staff to work on a twin-cylinder 350/500cc engine patterned around the same 90-degree, transverse Vee that had been contributing to the Moto Guzzi legend since 1965 (when the original 703cc V7 was officially introduced at EICMA).


It was a smart move—as often was the case with Mr. De Tomaso—unfortunately the project was plagued by the limited competence of the technical staff and additionally the technical shortcuts imposed by De Tomaso, who was not an engine specialist. And it didn’t help that the great Moto Guzzi Chief Project Engineer Giulio Cesare Carcano had resigned the moment Mr. De Tomaso took over.

Moto Guzzi V9 engine front CAD image
Moto Guzzi V9 engine front CAD image.Courtesy of Moto Guzzi

Among other things, the Argentine entrepreneur imposed that the con-rods salvaged from the failed Benelli 254 project be adopted on the new 350/500 twin. Inspired by the success of the Moto Morini 350, the De Tomaso technicians adopted a Heron type combustion chamber. But they did not do their homework properly in regards to the inlet ports and combustion chamber configuration (in order to obtain the correct swirl turbulences). In a comparison test that I ran at the time between the Moto Morini 350, the Ducati Pantah 350 XL, and the Moto Guzzi 350 Imola, the latter was dead last in all aspects of performance.

Moto Guzzi V9 engine 3/4 front-left CAD image
Moto Guzzi V9 engine 3/4 front-left CAD image.Courtesy of Moto Guzzi

Both the V35 (66mm bore x 50.6mm stroke) and the V50 (74mm bore x 57mm stroke) were plagued by unacceptable seizures. This was due to use of the way too short connecting rods sourced from the failed Benelli 254, which caused the piston to run through most of its stroke inside the crankcase—the cylinder being so short that it sported only two cooling fins. The next step was the evolution to V65, still solidly oversquare at 80mm x 64mm. Finally longer rods came into play.

The V65 was developed with both standard Heron type, and with four-valve-per-cylinder thermodynamics, the latter being credited with 60 horsepower. It was called the V65 Lario. Compact and light, the Lario was regarded by many as a junior Le Mans, but it never delivered the performance expected—its pushrod-and-rocker valve train was plagued by destructive valve-float problems, in addition to the chassis feeling hopelessly vague.

Moto Guzzi V9 engine 3/4 front-right CAD image
Moto Guzzi V9 engine 3/4 front-right CAD image.Courtesy of Moto Guzzi

From this sequence of false steps came the V75, the 744cc version that was created by stroking the V65 from 64 to 74mm, while keeping the 80mm bore. The rod’s center-to-center measurement was increased to 130mm, and performance was tamed to regain the reliability that is a long-established pillar of Moto Guzzi tradition. The V75 survived the multiple changes in Moto Guzzi ownership that occurred during the 20 years leading up to current owners the Piaggio Group taking over.

The bike was completely restyled and renamed the V7; it turned out to be the best selling of all the Moto Guzzi models. The engine was partially updated with the adoption of a single 38mm throttle body, and the related Y-shaped inlet manifold with very long runners—contributing to improved low-end torque and flexibility. Power was rated at 48 hp at 6,200 rpm, with 44.2 lb.-ft. of peak torque at 2,800 rpm.

Moto Guzzi V9 head combustion chamber
Moto Guzzi V9 head combustion chamber CAD image.Courtesy of Moto Guzzi

Recently, the Moto Guzzi small block underwent its first radical redesign in 40 years. The project started because it was necessary to increase displacement in order to retain the same power level while complying with the more stringent Euro 4 emission regulations. But things went much further.

Enter the new Moto Guzzi V9. The displacement was increased from 744 to 853cc by enlarging the bore to 84mm and increasing the stroke to 77mm. The crankshaft has been redesigned, but the connecting rods have remained at the same 130mm center-to-center measurement, which is getting a little short in relation to the new stroke. Dr. Giulio Cesare Carcano might not agree since he adopted 150mm rods on his original 70mm stroke, 700cc V7. But compactness has always been a priority with Guzzi’s V7 and V9 models.

Moto Guzzi V9 engine cutaway CAD image
Moto Guzzi V9 engine cutaway CAD image. Note squish area compactness of combustion chamber with piston at TDC (right).Courtesy of Moto Guzzi

The V9 engine is not only compact, but is also light at 96.3 lbs., only 5.5-lbs heavier than the V7. The thermodynamic design has undergone the most radical change. Gone is the Heron type combustion chamber, replaced by a honest-to-God hemi design.

Before going any further into this, I must underline that this is not the first time the small-block Guzzi V-Twin received a design of this type. Back in the late ‘80s, Umberto Todero, a long serving Giulio Cesare Carcano assistant, developed a special version of the V75. Given the 80mm-bore commonality with the original 700cc V7, he adapted the old design to the compact V75 to give life to a special version used for lightweight aircraft and drones. This very special edition of the V75 was said to perform fairly well, and was produced and sold in limited numbers to the Israeli Army, who used it to power a surveillance drone. Why it was never adopted on the Moto Guzzi V75 models is still a mystery.

Moto Guzzi V9 new double U-Joint final shaft drive
Moto Guzzi V9 new double U-Joint final shaft drive CAD image.Courtesy of Moto Guzzi
Moto Guzzi V9 new double U-Joint final shaft drive top view
Moto Guzzi V9 new double U-Joint final shaft drive (top).Courtesy of Moto Guzzi

The V9 uses much larger valves than the V7: inlet 40.5mm (compared to 33mm), exhaust 35.5mm (compared to 29mm). The valves are set at a 56-degree-included angle; geometry very similar to the one selected by Dr. Giulio Cesare Carcano for his original V7 and related evolutions. The combustion chamber features a neat and compact hemi profile, complete with the mandatory annular squish area. The compression ratio is 10.5:1, same as on the V7. Compared to the Carcano engine, the V9 uses polidyne cam profiles (in the ‘60s they were not there yet) featuring moderate lift—for easier maintenance and longer valve train life—and almost zero overlap.

This was chosen to create the most complete combustion of the inhaled charge, and to prevent any unburned hydrocarbons from escaping from the cylinders, in order to meet Euro 4 emissions with the help of a relatively small catalytic converter. The V9 uses an exhaust system that is almost identical to that of the V7, and also breathes through the same single 38mm throttle body.

Moto Guzzi V9 engine front view
Moto Guzzi V9 engine front view.Bruno dePrato
Moto Guzzi V9 power and torque curve
Moto Guzzi V9 power and torque curve.Courtesy of Moto Guzzi

It delivers 55 hp at 6,250 rpm with 45.7 lb.-ft. of peak torque at 3,000 rpm. The power and torque curves provide very smooth response over a wide rev range, which is what I experienced first hand riding the bike across the Alpine passes towering over Mandello del Lario. The Moto Guzzi team completed powertrain development by adopting a larger diameter, single-disc clutch, and a new double-U-joint driveshaft that clears the fatter rear tire. The chassis got a host of upgrades, as well, but the frame structure itself is basically unchanged. Wheelbase spans 57.7 in., up from the previous 57 in., and the front wheel has been pulled closer to the bike’s center of gravity by 0.8 in. This and the adoption of a swingarm which is 1.5-in. longer, biased more weight to the front. Combined with the reduction of steering rake from 27.5 degrees to 26.4 degrees, vastly improved the steering response, agility, and feedback. The Moto Guzzi V9 Roamer is the best lightweight Moto Guzzi ever.