Custom 1952 Triumph Thunderbird

Aftermarket parts redefine motorcycle styling

In our collecting and restoring world with a focus on “stock” motorcycles, it may surprise you to learn that period-manufactured parts from some of these companies, such as Bates solo seats, pillion pads, and MCM fork covers, have become extremely collectible, commanding top prices when available. That’s why, when Calgary, Alberta, Canada-based Max Linnell learned that this custom 1952 Triumph Thunderbird was on the market, he seized the opportunity. He knew it as the “MCM California catalog bike,” as it appeared in a circa 1973 printing of the MCM sales publication; the Thunderbird is loaded with period aftermarket components.

Max, 33, bought the Triumph in early 2024. He has been working on a custom Triumph chopper project for the better part of 10 years and had also acquired the bones of an early 1950s Triumph pre-unit, rigid frame project. Nearly desperate for something he could ride and enjoy immediately, he says that he happily lightened his wallet to obtain the ’52 Thunderbird. He sold his other pre-unit project and continues to spend time perfecting his unit construction Triumph chopper. He’s meticulous and he’s taking his time on that build.

“I normally wouldn’t ride someone else’s custom,” Max says, “that’s not really my thing. But the shop where I got the Triumph from had acquired the bike and had plans afoot to add a sissy bar and disc brakes — there was history behind the Thunderbird, though, and I wanted to save the bike.”

Triumph’s larger 650cc parallel twin 6T launched in 1950. The engine and basic running gear were based on its 500cc Speed Twin, which was revealed in 1937 for the 1938 model year. Not the first English manufacturer to construct a parallel-twin engine, Triumph was the first to truly capture the riding public’s imagination with one. Instead of a 500cc single, which was most prevalent at that time, the twin soon became the machine to have. Turner’s eye for detail helped, as the Speed Twin certainly looked fast standing still. The name helped sell the machine, too. Triumph’s response to American demands

After the Speed Twin in 1939, Triumph launched the sporting T100 — both were 500 twins, and they served most customers very well. In North America, however, dealers were clamoring for more power. In my book, Prairie Dust, Motorcycles and a Typewriter, I write about Saskatoon, Saskatchewan-based Triumph retailer J.B. Nicholson of Nicholson Bros. Motorcycles. Looking to the future of the motorcycle industry in the post-war era, on August 12, 1944, Nicholson penned a letter to Turner.

“We would like to suggest [Triumph produce a] 750cc O.H.V. Vertical Twin. Such a model will really be necessary to compete with the larger American models for fast cruising over long distances, a characteristic type of service machines are subjected to on American roads.” Attached were specifications detailing a large-bore Triumph. Nicholson envisioned the machine should have, among other details, a sprung frame with dual rear shocks and a telescopic fork. Powering the bike would be a 750cc twin, having a 7.5:1 compression ratio, with alloy cylinder barrel and head, featuring rocker boxes cast integrally.

Nicholson got a reply from Turner on September 29, 1944. Turner wrote, “Your suggestion of a 750 c.c. Vertical Twin, the specification of which you enclose, is very interesting. The difficulty of introducing a machine of this type is that it has only limited appeal; for instance it would not sell in our home market in any great quantities, and yet it would mean an entirely new production because our existing engine and gearbox would not stand stepping up to 750 c.c.”

Five years later, Turner changed his tune. By 1949, he’d taken the Speed Twin’s 500cc 63mm by 80mm dimensions to 71mm by 82mm to create the 650cc Thunderbird. To transfer the extra power to the rear wheel, Triumph slightly altered its gearbox for strength, but the bulk of the running gear remained the same. The gearbox was a separate unit to the engine, and all models so equipped became considered “pre-unit” once Triumph switched to full unit construction of its 650cc power plants in 1963.

Evolution of the Thunderbird’s design

Finished in a color Triumph called “Thunderbird Blue,” the 6T came equipped with a rigid frame and telescopic fork with headlight nacelle, and it could be purchased with the optional “Sprung Hub.” This sprung hub provided a modicum of rear wheel suspension travel, offering at most two inches of movement.

As attractive as the Thunderbird was, owners were quick to make changes. Max’s 1952 custom Thunderbird was featured in the April 1983 issue of Iron Horse magazine. In a story called “Forever Young,” the author wrote the machine had been “restored by Bill Lindsey 10 years ago.” Los Angeles-based Lindsey is quoted, and he says of the Triumph when he acquired it, “It was merely a 20-year-old bike that looked it.”

The feature reports that Lindsey took the Triumph completely apart to polish, clean, paint, and detail every component. He crafted his own gas tank mounts, a distinctive top head steady, and a side mount taillight/license plate bracket. Other details include a larger Amal Monobloc carburetor, new clutch and primary belt drive, and Harman & Collins high-lift cams. One note in the build specifications indicates the usual hollow steel rear seat tube had been replaced with solid bar.

Chrome plating was liberally applied to the oil tank and toolbox, timing and gearbox covers, engine and gearbox mounting plates, fork lowers, chainguard, and even the carburetor. From the MCM catalog are the 1-1/2 inch down flow exhaust pipes and the chrome fork covers. The solo seat and pillion pad are from the Bates catalog — all period-correct custom accessories.

Some pieces on the current Thunderbird are not the same as first built. For example, the front hub has been replaced with a one-year-only 1954 Triumph T100 and T110 “pie crust” hub, named for the shape of its distinctive scalloped brake drum edge. Also different is the ribbed primary cover; this was originally a chrome cover. Max was offered the chrome cover as part of the deal but says it was in rough shape, so he left it behind.

In the Iron Horse magazine article, the machine featured a later-model unit construction alloy cylinder head with a barrel painted silver to match. These items have been changed to an earlier alloy head, painted black, and the cylinder is also painted black. At some point after it was featured in the magazine, purple pinstripe flames were added to the deep gloss black paint job on the gas tank and rear fender. These changes aside, the Thunderbird is easily recognizable as the machine featured in the MCM catalog and remains faithful to the original custom.

About 10 years ago, a local Calgary collector bought the Triumph out of California. He rode the bike periodically, but it was prone to leaking oil, mostly from the gearbox. Soon, the bike was sitting idle and then passed along to the shop where Max acquired it.

Tracing the legacy of MCM

As popular as some of these aftermarket parts for older American and British motorcycles have become, information on the history of companies such as MCM is surprisingly scarce. There doesn’t appear to be a definitive online resource regarding MCM, but a friend was able to supply photos of period brochures. From these, we know that, circa 1951, the company was known as Motor-Cycle-Mufflers, or M.C.M. Mfg. Co. for short. Their business was based in Los Angeles, and products included exhaust headers and mufflers for 1951 and 1952 Triumph 5T (Speed Twin) and 6T (Thunderbird), and off-road Scrambles pipes for A.J.S., Matchless, and Velocette MAC. Also shown are headers and mufflers for a BSA A10, Indian parallel-twin, and Chief and Scout models. In another catalog, circa 1971, MCM is now in Whittier, California, and their products include pipes, mufflers, handlebars, and miscellaneous items from battery covers to fenders, fork covers, headlight brackets, mufflers, and muffler tips.

By 1978 to 1979, the MCM catalog indicates they were now in Anaheim, and were branding some parts with a Manx label. An introductory note states, “With more than 35 years experience (suggesting the company began operating around 1944), MCM is the oldest, most experienced manufacturer of after-market motorcycle accessories in the U.S.” However, it appears that by the early 1980s, MCM and other aftermarket exhaust manufacturers were facing mounting pressure from the EPA regarding noise and pollution controls. It’s unknown precisely when MCM ceased trading.

Max Linnell’s Triumph journey

Max is a mechanical engineer and says he didn’t spend a great deal of time around motorcycles as a young man. There was a dirt bike on his grandparents’ farm he would tinker with, but more importantly, he says his interest in old machinery was likely sparked by helping his grandfather, who was simply “keeping things together on a shoestring.” While in university, Max’s friend bought a street bike, and that spurred him to buy his own 1981 Suzuki GS750E.

“I figured I’d get my motorcycle permit, and I wanted something I could work on,” Max says of his decision to buy the Suzuki in 2012. He rode the GS750 for a year, and then over the course of a winter, stripped the bike apart down to the crank to freshen everything in preparation for the next riding season. “I successfully got it all back together, hit the starter button, and it fired up,” he explains. “I shut it off and was all excited because my friend was coming over to have a look at it because he didn’t believe that it ran. It didn’t start again.”

Exasperated, Max figured the problem must have been something electrical but was not able to resolve the issue on his own. He finally took it to a local custom bike shop. “It turned out it was a copper grounding strap on the starter motor, there was a hairline crack in it, and the starter motor would turn but then cause the crack to widen and disconnect the circuit — they charged me for an hour’s labor,” Max recalls.

While at the shop, though, the owner noted Max’s restoration efforts and offered him a summer job. Max took him up on it, viewing it as an opportunity to learn about motorcycles and what he was most interested in — building motorcycles. For minimum wage, Max did menial chores but was taken under the wing of the head fabricator. “We’d hang out after work, and he taught me how to weld and fabricate parts and pieces,” he says. “On their old Atlas lathe, I became the wheel spacer monkey and machined a lot of spacers.”

One of his co-workers had a Triumph chopper, which Max bought near the end of the season. “It was a sketchy home-built chopper, sketchy in all the ways you could imagine,” he says. It wasn’t safe, and ultimately the engine seized. “As I took the bike apart, the deeper I got into it, the worse it got,” he explains. Starting over with a new purpose-built rigid frame, this is the unit construction Triumph chopper Max has been building to his specification for more than 10 years.

Then he heard that this MCM Thunderbird custom was for sale. He bought it, and with it in his well-equipped two-car garage, he began working through it. “It didn’t take too much to get it running,” he says. “I made sure all the nuts and bolts were tight and headed out for a test ride.” The first time out, about 10 minutes down the road, it left him stranded. “It cut out on me, and every time, I’d take it home and fix something. Then I’d go out again, and 15 minutes later I’d be stuck somewhere else,” he laughs. Sometimes, it was just as simple as running out of gas, but the biggest issue was sorting out the Amal 389 Monobloc carb with the correct jets, and then getting it properly tuned.

He also took the time to sort out the leaking gearbox. With the inner and outer covers off, Max disassembled the gears and checked the bushings. All were good, but the ball bearing that supports the right-hand side of the main shaft was in poor condition. He sourced a new one, replaced it, cleaned everything, and re-sealed the covers with Hylomar M.

And he took the time to sort out the wiring. The front and rear lights mystified him, as they’d continually blow fuses until he uncovered the shrink wrap to realize some bright light had wired both the hot and the ground wires together. “It was never going to work properly that way, and who’d do something like that, right?” Max says.

Now with most of the Thunderbird sorted out, he’s been able to put more miles on it, including riding it the 35 miles each way to his job. It’s not too happy when the ambient temperatures are very high, but in cooler conditions, Max says that it’s a delightful runner.

“It’s a blast to ride,” he says. “With the Harman & Collins cams it’s got plenty of power and it’s really nimble and light. Fun in the city, with power for the highway and tons of torque.”

However, he’s planning on pulling the motor to go through it from the crank up with good friend and mechanical mentor Neil Gordon. Neil has spent decades building pre-unit and unit construction Triumph motors and has made much of his own tooling to help make the engines as bulletproof and oil tight as possible.

“For me, it’s an opportunity to learn some tips and tricks about the pre-unit Triumph motor,” Max says. “I’m really looking forward to spending time with Neil.”

Of his own appreciation for Triumph, Max says, “The Triumphs really have their magic, with a refined elegance when compared to other bikes. I see Triumph machines as very pretty and relatively affordable — and this custom Triumph just suits my personality. I’m thrilled that it’s mine.” MC