Moto Guzzi’s V2 Small Block

[Admin]

Moto Guzzi’s V2 Small Block has continually seen changes and refinement as the decades have passed, continuing to remain a staple of the fleet. (Bruno dePrato/)

Moto Guzzi is one of the legends of motorcycling, a marque easily as respected and loved as Harley-Davidson. The manufacturer was founded in 1921, when shipowner Mr. Emanuele Vittorio Parodi, along with his son and air force pilot Giorgio, got together with Carlo Guzzi to found Moto Guzzi in Mandello del Lario. But this maker of inarguably desirable bikes went through some very hard times, especially after World War II, and has had to rebuild its legend over and over again.

The Moto Guzzi factory in 1921 in Mandello del Lario. (Moto Guzzi/)

Just as Ducati had its foundational engineer in Dr. Fabio Taglioni, Moto Guzzi was blessed with the technical knowledge and motorcycle-industry experience one Dr. Giulio Cesare Carcano. Carcano created the best-performing Moto Guzzi racers and production models from the late 1930s through 1966, when he finally left the factory to which he had dedicated the largest part of his professional life. Dr. Carcano created winning single-cylinder Moto Guzzi racers, including the 350cc version that took Keith Campbell to the 1957 World Championship in the face of the much more powerful Gilera 350 Four, which could not counter a very light and agile single blessed by a very solid torque curve.

Keith Campbell in 1957. (Moto Guzzi/)

On the opposite end of the Moto Guzzi racer range, Dr. Carcano created the 500cc V8. For production, he designed a whole range of ultra-reliable Moto Guzzi singles from 250 to 500cc. When Moto Guzzi bowed out of competition, Dr. Carcano turned to the development of new production models intended to pull the Mandello del Lario make out of the doldrums in which the Italian motorcycle industry was foundering. Their market had been cut into by, of all things, the then-new Fiat 500 subcompact, which was cheap enough transportation to compete with small- and medium-displacement motorcycles.

The 500cc V8 designed by Dr. Carcano. (Moto Guzzi/)

To counter the 500, Dr. Carcano designed a 600cc, air-cooled, 90-degree V-twin that was more refined and much more powerful than the cheap parallel twin in the Fiat. The new 600cc V-twin was actually offered to Fiat as a prospective optional engine for a “sport” version of the 500. Tests were positive, but Fiat passed. Instead, they found a market in the Italian army, which had adopted Moto Guzzi’s Falcone 500 as their standard service motorcycle. They found the new compact V-twin was optimal for a half-tracked mountain vehicle, a sort of mechanized mule for alpine troops. Order numbers were limited, but adequate to start production and further develop and refine the engine that officially became the celebrated Moto Guzzi V7.

The V7 had a relaxed look that attracted traditional die-hard Moto Guzzi enthusiasts and that was reminiscent of the Harley-Davidson Duo Glide of the time. Three years later Dr. Carcano resigned as chief project engineer and Moto Guzzi hired Lino Tonti, who was not a certified engineer but known as a competent technician with a solid background. Tonti enlarged the V7 displacement to 750cc for the V7 Special, and then created the Moto Guzzi 750 Sport.

Moto Guzzi’s Small Block V2 has seen many changes, versions, and improvements since its introduction in the mid-’60s. (Moto Guzzi/)

In 1973 Moto Guzzi was acquired by Alejandro De Tomaso, who had acquired Benelli the previous year. This began De Tomaso’s controversial adventure with the two makes. De Tomaso was no engineer, and supposedly hated engineers due to their understandable practice of criticizing his technical decisions. From then on half-baked projects were the order of the day. A Honda CB500 Four engine was taken apart and used for the creation of the molds for the Benelli 504 and, with the crude addition of two extra cylinders, of those for the Benelli 756. De Tomaso also requested that the Benelli 504 be downsized to 350cc in order to power the Moto Guzzi 354. That project failed badly in the face of the Honda 350, so Tonti stepped in to suggest that Moto Guzzi create a small 90-degree V-twin to capitalize on the positive image of the V7 model range.

But the Moto Guzzi “Small Block” V-twin was not to be designed by the technicians in Mandello del Lario. De Tomaso wanted it designed at De Tomaso in Modena, perhaps because he wanted to check each developmental step. But the De Tomaso Motor Company had effectively no one with significant engine design or engineering experience, as De Tomaso cars were powered by Ford’s legendary 351 Cleveland V-8. There had never been a De Tomaso-designed engine. As a result, nobody knows exactly who designed the original Moto Guzzi V-twin. Indeed, the initial project was not particularly well refined.

The first production version came in the form of a compact 350cc unit of moderate potential powering a neat-looking runabout. The new V-twin featured a solid horizontally split crankcase, a forged crankshaft turning on plain bearings measuring 39mm at the distributor side and 41mm at the clutch side, giving a crank throw of 38mm; cap-type connecting rods were adopted. There was also a centrally located camshaft, cylindrical cam followers, steel pushrods and rockers, two valves per cylinder, parallel and perpendicular to the head plane, and, finally, a Heron combustion chamber.

So far so good, except for the fact that the project was developed with no solid engineering guidelines. The combustion chamber design had been adopted on the basis of the success of the Moto Morini 350cc and 500cc V-twins, designed by Dr. Franco Lambertini, a Heron specialist. His Moto Morini 350-500 V-twin was easily capable of exceeding a specific output of 100 hp/liter, as Lambertini knew how to play the high-performance combustion-chamber-turbulence game. However, De Tomaso decreed that the new V-twin would adopt the leftovers from one of his worst marketing failures: the Benelli 254, a four-cylinder 250cc model that he had expected to conquer the compact bike segment. But the thing never worked right and had a mean tendency to seize pistons. The market rejected it and the project was almost totally scrapped, except for the con-rods, which were forced into the Moto Guzzi V2.

The V35 had 30 hp and 20 pound-feet of torque. (Mary dePrato/)

With a 66mm by 50.6mm bore and stroke, the Moto Guzzi 350 V-twin could still swallow the short Benelli 254 rods, but the stroke-to-rod-length ratio was far from optimal and consequently secondary order imbalance was very high. Moto Guzzi introduced the new V35, announcing a power output of 30 hp at 7,800 rpm, but that was hard to believe in light of the claimed peak torque of 20.2 pound-feet at 6,500 rpm. In reality the Moto Guzzi V2 limped along all its life. Good engines come from neat engineering projects, not from patched-up “creations.” The factor that kept the unit alive in its original 350cc displacement was that the numerous model variations it powered were all rather pleasantly styled, with the exception of the short-lived 1987 V35 Florida custom. The V35 was fairly big and heavy for a 350cc-displacement engine, though the crankcase had proved one of the best points of the whole project, being capable of standing much higher loads.

The 500cc V50 edition was introduced in 1977 by increasing bore and stroke to 74mm and 57mm, respectively; with a compression ratio of 10.4:1 and fed by a pair of 24mm Dell’Orto carburetors, the engine was claimed to generate 48 hp at 7,500 rpm, but this again was hard to believe. Bore and stroke measurements aside, the engine design was basically unchanged.

The 500cc V50 Small Block was introduced in 1977. (Moto Guzzi/)

And that includes the con-rods, still the Benelli 254 leftovers despite the increased stroke. This caused more than one reliability problem, since the cylinders were very short and the pistons traveled inside the unexposed segment of the barrel, causing the engine to become very hot when working at high rpm for extended time. The stroke-to-rod-length ratio problem was closed when the Moto Guzzi V2 was enlarged to 650cc by boring it out to 80mm and stroking it up to 64mm. The adoption of adequately sized rods, now measuring 120mm center to center, was apparent in the increased height of the cylinders, now featuring seven cooling fins in place of the previous three. At long last the beleaguered Moto Guzzi V2 Small Block got its rods right, finally bringing one of the most tragic and operatic episodes in all of Italian history to a triumphant and satisfactory denouement.

The largely revised 650cc version of the engine was slowly emerging as the real lightweight partner to its larger brother, which had in the meantime grown first to 850cc and then to a full 1,000cc displacement. With a properly proportioned crank assembly, the 650 was smoother and more reliable. Fed by two Dell’Orto PHBH 30 carburetors and with a 10:1 compression ratio, the V65 was claimed to deliver 52 hp at 7,050 rpm with a 40 pound-feet of torque peak at 6,000 rpm. Given the moderate weight at 368 pounds, the new V65 turned out to be a gratifying tourer with a top speed in the region of 115 mph and solid throttle response from 3,000 rpm up.

Moto Guzzi developed a number of model variations around the V65 unit, including fully dressed custom touring bikes that enjoyed a mild success with the public. The V65 Lario was expected to set a solid mark in the domain of the intermediate-displacement sportbikes, as it was a neat-looking bike powered by a special four-valve edition of the V65 twin.

Riding the V65 Lario in 1984. (Mary dePrato/)

There was much cheering at the unveiling of the V65 Lario at EICMA 1983. The motorcycle promised to renew the myth of the V7 Sport. But not so fast; the four-valve V-twin featured the same basic valve train, featuring cylindrical tappets, pushrod, and sleeve-type rockers crowded inside the heads. Moto Guzzi claimed 60 hp at 7,800 rpm and 40.1 pound-feet of torque at 6,000 rpm. The Lario went into production in the second half of 1984…and had disappeared by the end of 1985. The valve train was so oddly put together that the relationship of the pushrods and rockers was all wrong, causing flexing that developed awful frequencies at higher revs, destroying the valves and, as a consequence, the pistons as well.

The four-valve head of the V65 Lario was an overcrowded mess that destroyed valves due to flex and vibration at higher revs. (Bruno dePrato/)

Moto Guzzi went back to the traditional two-valve heads on the V65 and on the subsequent V75, an engine that was regarded as being at the displacement limit for the unit. The V75 debuted in 1989 as a stroked V65, featuring the same 80mm bore with the stroke grown from 64 to 74mm. Moto Guzzi finally claimed a credible 45 hp at 6,800 rpm from a unit with a compression ratio of 9.7:1 fed by two PHBO 30 Dell’Orto carburetors. Peak torque was a moderate 43.8 pound-feet, but at only 3,200 rpm. In 1989, the four-valve heads resurfaced for special editions of the NTX enduro model intended for the Paris-Dakar rally, but the attempt never reached its target.

A longer V75 connecting rod (left) next to a V65 rod. (Bruno dePrato/)

Meanwhile, Moto Guzzi suffered an undeniable decline throughout the ’90s due to an increasingly erratic management from De Tomaso. This finally ended when Moto Guzzi was acquired by Ivano Beggio’s Aprilia Group, but things did not immediately improve at Mandello del Lario. Beggio and his team were focused on the models powered by the “Big Block” V-twin, and the V75 was merely restyled into the Breva V750 runabout. The engine evolved from carburetors to fuel injection with a slight power increase to 48 hp at 6,200 rpm. The Breva V750 was styled smartly, maybe even too smartly for a Moto Guzzi, and its 750 V-twin delivered 41 hp. The chassis was new and featured a radical steering geometry that received controversial comments due to a steering axis set at 28 degrees.

For beleaguered Moto Guzzi the real turning point came in 2004, when the Piaggio Group acquired the whole Aprilia Group and Moto Guzzi with it. The Piaggio engineering team took the V75 apart and duly analyzed it, while the styling department decided to adapt the most classic V7 750 Sport styling to the 750cc, small-block, V-twin-powered V7, setting the stage for the V7 Classic.

The Breva V750 was a departure in styling for Moto Guzzi. (Moto Guzzi/)

In 2012 the Euro 3 emissions regulations came into force and the engine received the first of a series of fundamental upgrades. The Piaggio technicians developed a new induction system featuring a single 38mm throttle body and a Y-shaped inlet manifold. The combustion chamber kept the Heron-type design, but new higher-quality pistons allowed a compression ratio bump to 10.2:1. Peak power of 48 hp at 6,200 rpm and 40.3 pound-feet peak torque at 5,000 rpm were claimed; the new induction system and higher compression ratio definitely generated a much flatter torque curve, and the engine performed smartly in all road tests.

At this point let me say that I still wonder why the Piaggio technical team did not try to improve the 750 V-twin by analyzing and evolving the design of the Heron chamber to improve its turbulence game. The 80mm bore would allow plenty of opportunities to reposition the valves, which were aligned on the main diameter of the bore with the inlet runner coming in straight. This did not result in the conditions needed to generate the proper swirl turbulence necessary for a Heron combustion chamber to deliver optimal combustion and maximum efficiency. The Heron design requires strong, well-managed turbulence more than other combustion chamber configurations. The Moto Guzzi technicians had only to take a look at the Heron combustion chamber of the Moto Morini 500 V-twin that was then delivering 48 honest horsepower. Perhaps Piaggio was already thinking of its next hemi head.

The 2019 Moto Guzzi V7 III Racer. (Moto Guzzi/)

The new hemi head debuted in 2016 in order to bring the engine in line with the new Euro 4 regulations, and may represent the ultimate evolution for the Moto Guzzi Small Block V-twin. The head was just the beginning of the final evolutionary process. In combination with the new head, the displacement was increased to 853cc by enlarging the bore to 84mm and increasing the stroke to 77mm. To fully comply with the Euro 4 regulations, the new head incorporated a secondary air circuit to more thoroughly treat the exhaust gases in the catalytic converter. The valve train was revised by fitting the tappets with roller-type cam followers, which not only reduced the frictional losses but allowed the use of more advanced cam grinds. The new cams feature fairly high lift and very short overlap to drastically reduce the emission of unburned hydrocarbons.

The combustion chamber features a compact hemi profile with the valves set at a 56-degree included angle. The valves measure 40.5mm for the inlet and 35.5mm for exhaust, much larger than those of the V7 Heron, which were 33mm and 29mm, respectively. Despite the larger valves, the combustion chamber profile includes a neat annular squish area for a better control of turbulence. Compression ratio is a solid 10.5:1, same as on the V7. The V9 still breathes through a single 38mm throttle body and Y-shaped manifold. Power went up to 55 hp at a moderate 6,250 rpm and 45.7 pound-feet of torque at 3,000 rpm. These numbers underline the great flexibility of the new engine and its ability to deliver positive performance forth from Mandello del Lario unto the very ends of the Earth. A new larger-diameter single-disc dry clutch was adopted, along with a new final transmission featuring a shaft drive with two U-joints for much smoother functioning.

The V9 was just a safe step to reach the ultimate target. Enter the V85. The V85 is what the Moto Guzzi Small Block V2 should have been from the beginning, not in terms of the displacement, but in the rigorous engineering and research applied to the whole project down to every last component. Never mind, for once, the bore and stroke numbers; the V85 is an even more radical evolution of the first-edition V9.

To achieve much higher power numbers it was necessary to make the engine reliably rev much higher. Therefore, Piaggio technicians have recalculated the crankshaft, slightly increasing the diameter of crank and main end journals and related bearings, now measuring 40mm and 43mm on the distribution and clutch sides, respectively, up from the previous 39mm and 41mm. Crank throw diameter has also been increased, from 38mm to 40mm. The resulting crankshaft is more than adequately strong and rigid, even in combination with the V9/V85 77mm stroke, since even here the main and the crank journals overlap by a few millimeters at both ends. The lubrication system has further evolved with the adoption of a semi-dry sump and two pumps. The sump received larger cooling fins to improve oil cooling. This way there was no need to add an oil cooler. An accurate study addressed to improve the crankcase ventilation and reduce oil splashing further improved the reliability of the whole lubrication system and the mechanical efficiency of the new unit.

The first-edition Euro 4 homologated V85 TT unit delivered 80 hp at 7,750 rpm and 59 pound-feet of torque at a moderate 5,000 rpm. Now the unit has been updated to the Euro 5 standard with no change to displacement and still delivers 78 real horses—a remarkable result.

The Moto Guzzi V85 TT. (Bruno dePrato/)

To become the new V85 TT, the V9 was redesigned in all the major components. The rods come from new forgings and are reportedly lighter and stronger. They still measure 130mm center to center, which—as careful readers will no doubt realize by now—is a little on the short side in relation to the 77mm stroke. Piaggio technicians wanted to keep the engine as compact as possible, though at the possible cost of higher secondary-order imbalance. The valve train was completely recalculated both in cam grindings and the structure of cam followers, pushrods, and rockers. Pushrods of various structures and made from a variety of materials were tested to obtain the most stable and reliable transfer of the exact lift from the cam profile to the valves. Finally, solid pushrods made from high-tensile aerospace aluminum alloy 7075 were selected for their low inertia and the positive results they granted in terms of performance and reliability. To obtain the highest possible volumetric efficiency from a two-valve design, a 47mm titanium inlet valve was adopted. The V85 breathes through a 52mm central throttle body and related Y-shaped manifold.

The last step in the evolution of the Small Block is the V9. This is not an upgraded edition of the previous V9, but rather a more accessible edition of the V85. Piaggio technicians have distilled that engine into a new general-purpose unit intended to deliver a substantial increase in performance level while keeping the price competitive.

Moto Guzzi’s Small Block V-twin evolution is represented by the new V9. (Moto Guzzi/)

The cylinder head retains the layout of the V85 unit, but the inlet valve is stainless steel, the central throttle body is 38mm in diameter, the cams have milder profiles with almost no overlap, and the pushrods are steel. Yet the new V9 delivers a claimed 65 hp at a moderate 6,800 rpm, 10 hp more than the previous version. More remarkable is an improved torque curve, climbing from the previous claimed 45.7 pound feet at 4,000 rpm to 53.8 at 5,000, a clear improvement. In order to make the V9 both more accessible and more competitive, Piaggio decided to drop the crankshaft’s traditional forged one-piece construction (though this is retained in the V85) and adopt a press-fit crank assembly with one-piece con-rods. The new crankshaft features a slightly leaner crank throw, 38mm in diameter instead of 40mm for the solid forged unit, but Piaggio says the assembly remains fully reliable due to proprietary technology developed to ensure a very solid and stable assembly.

Gone is the 750cc version of the Moto Guzzi Small Block V-twin. Production will focus solely on the 853cc engine. The V7 and V9 models differ only in styling, with the V7s retaining their classic and very elegant look and the V9 more along the lines of a custom. Moto Guzzi celebrates its 100th anniversary in 2021, and to make the celebration memorable, a totally new V-twin will be unveiled, displacing at least a liter and featuring liquid-cooling and four valves per cylinder. Given the performance achieved by the V85 TT unit, chances are that the Moto Guzzi Small Block V-twin will remain in production for years to come. One still hopes that someone in the marketing department will see the light and a V85 Sport will become reality, perhaps in metallic light green with a red frame holding the best available components. Motorcycling is made of special memories, passionate dreams, and perfect replicas that revitalize immortal models by applying solid but invisible technological updating.

View the full article