1937 Gnome-Rhone AX2

Staring at images of this 1937 Gnome-Rhone AX2 800, it’s easy to get lost in the myriad details of its design.

The relative age apparent on many of its components only adds to the allure — what stories could this machine tell? Unfortunately, this Gnome-Rhone’s backstory is lost to history, but Jim Balestrieri of Wisconsin’s Throttlestop Museum is certainly familiar with its most recent past.

Always on the lookout for motorcycles to add to Throttlestop’s growing collection of diverse machines, in early 2021 Jim found the AX2 800 offered for sale by Yesterdays Antique Motorcycles in the Netherlands. “I’m fascinated by motorcycles with a military connection, and Gnome-Rhone is just one more company with that background,” Jim explains. “And I like larger, more robust bikes, and the AX2 is a big mama.” Although he’d been looking for a Munch Mammoth on Yesterdays’ site, the AX2 piqued his interest. Instead of locating a Munch, Jim purchased the Gnome-Rhone. It landed Stateside in mid-August 2021.

Looking back

According to the website amicalegnomerhone.net (or, loosely translated, Friends of the Gnome-Rhone), the company was at first two competing manufacturers of industrial and aircraft engines. First, there was Gnome. In 1895, French industrialist Louis Seguin took over a factory near Paris, in Gennevilliers, that produced metal pipes and other products. As interest in internal combustion engines intended for industrial applications began to increase, Louis established the Société des Moteurs Gnome in the Gennevilliers plant.

There, the firm built a single-cylinder industrial engine under license from the German-based company Gnom. The moniker Gnome was derived by simply adding an “e” to Gnom. By 1905, the company had become a large-scale producer of gasoline-powered engines, and Louis’s brother, Laurent, joined the firm. Shortly after that, Gnome ventured into the field of aviation, engineering and constructing radial engines where the crank was fixed and the cylinders revolved. These engines became favored not only by the French military, but other countries where Gnome’s designs were built under license.

Next, there’s the Rhone side of the name. Engineer Louis Verdet also designed radial aircraft powerplants but wasn’t quite the powerhouse of Gnome. Yet, he operated his Le Rhone company as a rival of Gnome’s until the larger, more politically well-connected firm sought a merger. Negotiations went on for months in 1914, which ultimately led to the creation of the Société des Moteurs Gnome and Rhone. During World War I, from 1915 to 1918, Gnome-Rhone’s factories churned out aircraft engines. However, at the cessation of hostilities, radial powerplant orders plummeted, and Gnome-Rhone was forced to diversify, turning its attention to other industries, including automobiles and motorcycles.

Regarding motorcycles, in 1919, Gnome-Rhone took up building, again under license from a foreign firm, the British-devised 400cc ABC flat-twin machine. Originally designed by Granville Bradshaw, Gnome-Rhone engineers were quick to upgrade the ABC design, taking the engine to 500cc and converting the machine to metric specification. In 1920, customer orders for the flat-twin machines began to be filled, and, in the years following, Gnome-Rhone engineers developed a wide range of single-cylinder motorcycles, both 2-stroke and 4-stroke powered.

Moving on

Gnome-Rhone quit producing horizontally opposed engines for its motorcycles around 1924 but returned to the platform in 1930 with its V2 model. Powered by a 500cc flat-twin engine, the V2 featured shaft final drive and a stamped steel frame and forks. It’s obvious the model took some of its inspiration from similarly designed BMWs. The German company had introduced its R11 sidevalve and R16 overhead valve models in 1929, equipping them with pressed steel frames and forks to take the additional power of their 745cc flat-twin engines and the extra weight of a sidecar.

Gnome-Rhone’s V2 led to the CV2, with overhead valve gear; it was launched in 1932. Intending to build a fast and somewhat luxurious sidecar tug, in 1935, Gnome-Rhone debuted the model X. Powered by a 724cc OHV flat-twin with a 4-speed gearbox, still with shaft final drive all in a pressed steel chassis, the X was hitched to a Bernardet Sport sidecar tub rolling on a purpose-built chassis. The X could be had with an optional foot-shift gear control, and the model won acclaim for both its turn of speed and its reliability.

For military testing, from the X, Gnome-Rhone built the XA — A for “army.” This machine featured shaft drive to the sidecar wheel (all three wheels were interchangeable), and engine capacity had been enlarged to 750cc. Apparently, fewer than 500 XA models were built before the company developed the AX2 in 1936. The AX2 was meant for military or police service and was powered by a larger 800cc sidevalve flat-twin engine.

François-Marie Dumas, who hosts the moto-collection.org website, writes that the AX2 was “Effective everywhere without being brilliant anywhere.” At 316 kilograms or nearly 700 pounds, the AX2 still featured the pressed-steel frame and fork with rigid rear and front suspension affected by rubber “springs.” The engine boasted square measurements, at 80mm by 80mm for bore and stroke and could produce 18.5 horsepower at 4,000rpm. The 4-speed transmission was shifted by hand, and some AX2s featured a reverse gear. There was also a mechanism that allowed a rider, while seated, to engage or disengage the driven sidecar wheel. Drum brakes were in the 19-inch wheels, all of which were interchangeable.

Gnome-Rhone built the AX2 until 1945, and there does not seem to be a consensus regarding the overall number produced. Some claim it was thousands, while others suggest it was far fewer as the result of slow production and, in 1940, damage at the Gnome-Rhone factory due to bombing.

After the war, Gnome-Rhone became a part of the Société Nationale d’Étude et de Construction de Moteurs d’Aviation (SNECMA), a nationalized company that included several other motor companies. As a result, Gnome-Rhone discontinued production of its large flat-twin motorcycles, concentrating instead on smaller-bore single-cylinder machines in a variety of engine sizes. By 1960, however, Gnome-Rhone had quit motorcycle production altogether. Under the SNECMA banner, the company continued to develop engines for aircraft and spacecraft applications.

Our feature bike

Now, returning to the story of Jim’s AX2. “One of the nice things about Geert’s (Versleyen, of Yesterdays Antique Motorcycles) machines is most of them run,” Jim says. “And he’ll tell me if something doesn’t. When we got the Gnome-Rhone, we initially assessed just what we had, and we had to make a decision about restoring it or leaving it as it was. It did not come with a sidecar, and I think it might have been used as a police bike. It has faded dealer or service company decals on it, which are pretty much illegible.”

He continues, “Someone relocated the speedometer to that hard-mounted panel; that’s not original, and it’s rough, and it’s rusty, and it’s been repainted, but we thought it was really pretty awesome that way. So, we chose to get it running and then see where we’d go from there.”

Working as a mechanic at Throttlestop is 32-year-old Ryan Luft. He picks up the story and says, “The Gnome-Rhone didn’t have any spark when we got it. The bike has a magneto ignition, and I temporarily converted the ignition from magneto, which is a Magnéto France unit, to a 6-volt battery and coil system, simply using the mag as a distributor. I did a quick clean of the Solex carburetor, and I got it to fire up and idle nicely on the bike lift.”

With that success, Ryan removed the magneto and sent it to Bill Lopoulos of Bill Lopoulos Magneto Parts in Northbridge, Massachusetts. There, it was found the armature was in good condition, but the coil needed to be rewound. With the renewed magneto in hand, Ryan reinstalled it.

“There’s not a ton of information out there about this motorcycle, and I’m sure there are people far more educated than me about these bikes, so I had to guess where the correct timing might be,” he explains. “I set it close to where Brit-bikes fire, and I got it so it would fire up and run using gas from a remote tank. The Gnome-Rhone’s tank was filthy, so I removed it to have it chemically dipped to strip both the inside and the outside.”

On the AX2, the gas tank is not actually visible. What one sees is a tank cover, and the tank itself sits down between the upper pressed steel frame rails. “It’s really a pain to get that tank out, but with the inside cleaned up and the tank back in the bike, I soldered up a copper fuel line with fresh fittings and installed a new brass lever-style petcock. The fuel system is quite solid now.”
Meanwhile, the tires on the Gnome-Rhone, although certainly not original to the machine, helped give the motorcycle its sweaty and well-used appearance. Replacing them would have ruined the overall look, so Ryan only replaced the inner tubes.

“They hold air, and if the bike had a brand-new pair of Dunlops or something on there, it would look silly,” he says. Now, the Gnome-Rhone is a good runner, and both Jim and Ryan have ridden it. They don’t go far, staying very close to the Throttlestop building and not venturing onto public roads.

“It has an ignition advance and retard lever on the left bar, together with a hand clutch lever,” Ryan says. There’s a third lever on the left, which is not connected. Ryan says, if he had to guess, that it’s likely the original hand clutch lever, as the one with the cable appears to be an aftermarket item.

Ryan adds, “On the right, there’s the front brake lever, throttle, and a control to manually dip the headlight.” The Bosch headlight, Jim explains, was added by a previous owner to personalize the machine.

“To start the AX2, you turn on the fuel, give it a little choke (a lever under the left side top frame rail), a little touch of throttle and kick down on the kickstart lever. That’s on the left side of the machine, and it’s similar to kicking over a BMW flat twin in that the action of the lever is perpendicular to the motorcycle. One kick, and it usually fires up and then runs like a generator.”

There’s a foot clutch lever on the left, as well, and the right-side hand shifter moves in a gate with an H-pattern. Ryan says the lugs for mounting a sidecar are all present. Although he’s not removed the cap on the right-hand side of the rear drive, he’d like to think that underneath it there are splines to accept a shaft to a sidecar wheel.

“We keep it fueled up and have it in the event space at Throttlestop, where we can fire it up occasionally. It’s a conversation piece that runs,” Jim says, and concludes, “We just wish it could tell us more about its past because it’s obviously had a unique one.” MC