Greg Williams tells us all about an unusual motorcycle with a unique front suspension.
by Jeff Barger
With a machine like this 1947 FN Model 13, a good portion of the story is obviously going to be about the unique front fork.
Owner Jim Balestrieri of Wisconsin’s Throttlestop Museum is, of course, intrigued by FN’s engineering. But he’s also just as pleased to know his rare-for-North America FN M13 was restored by 27-year old Donovon LeVan, lead technician at Retrospeed in Belgium, Wisconsin.
“I always hear people saying younger people today don’t understand older technology and don’t have the drive to learn,” Jim says, and continues, “but it’s unwarranted to talk that way. There are exceptions who are trailblazers in the younger generation who are not all into electronics or the newest technology.”
Take Donovon for example. He enjoys working on something from a bygone era and understands the intricacies of carburetors and vintage ignition systems. Donovon grew up on a small farm in northwest Wisconsin, and got his first bike, a 1975 Yamaha XS650, when he was 15. Stored for years at the back of an old pole barn, the XS650 was dragged home. With help from his uncle, Donovon got the bike running, and he rode it for several years.
After high school, Donovon moved to Milwaukee to attend architecture school. Once there, he says he quickly discovered it wasn’t a career he wanted to pursue and remembering his interest in tinkering with the Yamaha, instead got a motorcycle repair technician degree online through Penn Foster.
“Brady (Ingelse, Retrospeed founder and owner) hired me before I’d finished the program,” Donovon says. While the motorcycle repair program gave him a good grasp of the basics, “Most of what I’ve learned about restoration has been here at Retrospeed working hands-on with Brady.”
Since starting at Retrospeed in 2016, Donovon’s been involved in the concours restoration of five motorcycles. With each project, he became more independent, and Jim’s FN was completed largely on his own.
“The FN was a bike none of us had ever dealt with before,” Donovon explains.
- Engine: 444cc air-cooled sidevalve 4-stroke single-cylinder, 84.5mm x 80mm bore and stroke, 11hp, compression ratio unknown
- Top speed: 62mph (100kmh), est.
- Carburetion: Amal 276 Pre-Monobloc
- Transmission: 4-speed, oil bath clutch, unit construction
- Electrics: Battery ignition with Miller dynamo
- Frame/wheelbase: Tubular steel cradle frame, 55.5in (1,410mm) wheelbase
- Suspension: “Pulled wheel” or “wheelbarrow fork” front, Neiman rubber band spring rear suspension rear
- Brakes: 4in (101.6mm) drum front, 6in (152.4mm) drum rear
- Tires: 3.25 x 19in Duro HF308 front and rear
- Weight (wet): 310lb (141kg)
- Seat height: 30in (762mm)
- Fuel capacity: 4gal U.S. (15ltr)
The beginnings of FN
Made by Belgium’s Fabrique Nationale d’Armes de Guerre, the company’s full name literally translates as the “national factory for the weapons of war,” but is commonly known by the initials FN. These days, the brand is part of the Herstal Group, whose website notes that FN was founded in 1889 to supply 150,000 Mauser rifles to the Belgian military under a license from the German maker.
FN went on to become one of the world’s leading firearms manufacturers, but also quickly saw the need to diversify its business to carry it through peaceful times when military contracts dried up.
In April 1896, FN company directors shifted some production capacity to the manufacturing of bicycles, including an interesting line of shaft-driven two-wheelers before progressing to automobiles in 1899, followed by motorcycles starting in 1901. That early machine was essentially a chain-drive FN bicycle featuring some reinforcement to the frame to support a 133cc, 1-1/4 horsepower single-cylinder 4-stroke engine. FN produced 300 examples of this motorcycle from 1901 through 1902.
From singles to multi-cylinder machines
Achieving a level of success with single-cylinder motorcycles, which they continued to produce, FN worked with engineer Paul Kelecom to design a 4-cylinder model. Their concept, unveiled in 1904, had the 4-cylinder engine in-line with the frame, and featured shaft final drive and many other interesting attributes. FN improved the Four over the course of several years but quit production of the models in 1926, leaving just the singles in their lineup.
These singles, up to 1924, had been equipped with shaft final drive. This changed with the introduction of the M60 350cc single, which was less complicated, lighter, and less costly to produce as FN combined the engine block with the transmission, building a “unit style engine.” Also, the shaft final drive was replaced by chain.
On the M60, the crankcase/gearbox was split horizontally. There was a 3-speed transmission with gear-drive primary and chain final drive, with gear shifts made by a short right-side hand operated lever.
By 1935, FN offered a wide range of M single-cylinder machines, including a 250cc 2-stroke. After the Second World War, FN continued to develop only single-cylinder motorcycles, and launched the M XIII, or Model 13. In 1947, the year of our featured machine, this was offered as a 350cc and 450cc sidevalve single, as well as a 250cc and 350cc overhead valve single. A semblance of rear suspension was introduced, as the rear frame section pivoted behind the engine and was sprung with rubber just under the seat. But what was really unique about the first M13 was the unconventional front fork.
In Guy De Becker’s book Quand la FN Avait 2 Roues (loosely translated, “When the FN Had Two Wheels”) the author notes, and this is loosely translated from French, “The front fork is indisputably original,” he explains of the design. “Its principle of operation remedies the various drawbacks of the usual systems. The front fork of a M XIII can be broken down into two distinct elements: the directive fork, controlled by the handlebars, and the fork proper that literally pulls the front wheel.”
De Becker says design work on this pulled swingarm fork was done prior to the World War II. At a time when many manufacturers switched to hydraulic dampers, FN promoted this new fork that appears outstandingly complicated as a series of tubes and springs conspire to steer and suspend the wheel. A long swingarm pivots in front of the wheel, and using the example of a wheelbarrow, it’s easier to pull a single-wheel up a curb, rather than the opposite — push a single wheel up a curb.
Image by Jeff Barger
In 1949, the M13 fork was changed again with rubber rings replacing the springs. FN produced an offroad version of this fork, too, and although De Becker notes the design worked quite well, the buying public never accepted the technology. A hydraulic fork was installed for 1952, when the M13 was available in 250cc and 450cc overhead valve versions, and a sidevalve 450cc.
FN quit production of the 250cc overhead valve and 450 sidevalve M13s in 1957, followed in 1959 by the 450 overhead valve model. At that time, FN sold only small displacement 2-stroke mopeds, or cyclemotors as they were called, and 2-stroke motorcycles, the largest of those the M22 250. By 1967, FN was winding up all motorcycle production and returned to its origins, focusing on firearms.
Finding this FN
Jim, of the Throttlestop Museum, says he’s long been a fan of the early FN 4-cylinder motorcycles and owns several of them. But when he came across this 1947 M13 online being offered by Yesterdays Antique Motorcycles (yesterdays.nl), it piqued his interest.
“I was aware of this unusual front end produced by FN,” Jim explains, and adds, “Although I wasn’t out hunting for one specifically, when this one popped up, I jumped on it. I wasn’t too concerned about condition because it looked like all of the parts were there.”
As delivered, the FN was presentable and Jim says he would have been fine leaving it alone, but ultimately decided to have Retrospeed perform a complete concours restoration.
Donovon picks up the story.
Image by Jeff Barger
“It came into the shop as a runner,” he says. “It had been restored at some point in its life, but restored incorrectly — there was a lot that wasn’t right. The first place I started was looking for literature. I sent email after email to people, and one of the only replies I got was from Jacques Maertens, the man behind the FN Oldtimer Motorcycles website. He sent me all these PDF files with hundreds of pages associated with FN and I spent hours poring over those documents looking at M13 specs and details.”
Using the frame number, Jacques was able to determine Jim’s M13 was produced on May 30, 1947, and was originally sold in Bruges, Belgium. What kind of life it lived after that is unknown, but in Donovon’s hands he began the process of correcting existing problems.
“Before we tear down a motorcycle, we fix as many issues as we can,” he says.
Where to start?
The center and side stands didn’t work properly, and neither did the rear suspension with its rubber bands. New mounting tabs for the stands were fabricated and a source for rubber rings was found in Poland. The tire pump brackets located on the front frame downtube were missing, so Donovon made and installed replacements.
After that, the motorcycle came apart. Inside the 450cc sidevalve engine, the valves, which are the same size both intake and exhaust, were shot. Replacements could not be found, but it was determined stainless steel exhaust valves from a 1998 Chevrolet Corvette would drop into the guides. The engine cases were tumble polished while the cast iron cylinder was powder coated black. New crank bushings were machined to suit, and all new bearings went in the transmission. Donovon honed the cylinder and used the same piston but installed new rings.
“It’s a very simple engine once you’re inside,” Donovon says. “Timing the crank and cam was very clear and easy to do, but one of the most difficult things was correctly timing the gearshift mechanism.”
Air and fuel are mixed in an Amal 276 pre-Monobloc carburetor, and this was available new from Burlen Fuel Systems in the U.K.. A complete exhaust system in bare steel was sourced from Oldtimer Garage in Poland, and Retrospeed had this chromed.
The wheels were stripped and the rims rechromed and the centers painted in the correct FN blue. With few original M13s in existence, getting the correct blue color was difficult. And all period photographs are in black and white. Thankfully, Jacques came to the rescue. He has an old gas tank with remnants of original FN blue, and it was color matched to provide the paint for this restoration. Spoke nipples were unplated brass, and Donovon says it was hard to find a company willing to sell bare brass nipples. Eventually, nipples were located in the U.K at Central Wheel Components. The hubs were treated to new bearings, but the brake shoes were deemed to be in good condition and, after cleaning, were reinstalled.
The steering head bearings were in deplorable condition, and a search for replacements yielded no results. Retrospeed’s machinist was able to recreate a set, hardening the cups and cones before chrome plating. “The stack height of the headset is extremely critical, and he knocked them out of the park,” Donovon says of the bearing set.
The FN’s long swingarm front fork pivoted on bushes made of a composite material. These bushings had mostly disintegrated, and Retrospeed machined appropriate replacements in bronze. With those in place, and the new headset installed, Donovon reports the front end went together with little drama. All frame and fork components were painted black prior to assembly.
Image by Jacques Maertens
The gas tank had a dent that needed to be lead filled and metal shaped before chroming and painting. As purchased, the paint scheme was incorrect for the ’47 M13. Photos were studied to provide the proper layout that’s striped in a yellow/gold while FN decals were reproduced for Retrospeed.
After cleaning the saddle pan and painting it black, it was sent overseas to Brussels for a new cushion and cover. Electrical components were originally produced by Miller, a British brand and a contemporary of Lucas. Finding parts for the Miller headlight, taillight and ignition system did not prove difficult. Donovon created a replacement wiring harness following the old loom as a pattern, and upon completion, everything works as expected. Finally, Jacques helped source rubber pieces such as the correct footpeg covers, grips, and gas tank knee pads.
Donovon has ridden the machine in its restored state. The young technician says it’s kind of a clumsy bike to ride because the steering is rather heavy, and the rubber rear suspension is bouncy. “It’s like a small sailboat,” Donovon says, and concludes, “But the bike speaks to me because it’s so unique, and riding it connects you to a time when FN engineers were trying to improve the motorcycle experience.” MC
Updated on Feb 5, 2022 | Originally Published on Feb 3, 2022
This 1951 Fabrique Nationale de Herstal Military M13 was one of hundreds of classic motorcycles at the Barber Vintage Motorsports Museum in Birmingham, Alabama.