1969 Bridgestone TMX-7: On Road & Off

Top speed: 60mph (Est.)
Carburetion: 18mm Mikuni
Transmission: 4-speed, left foot shift
Electrics: 6v, magneto ignition
Frame/wheelbase: Single downtube cradle with swingarm rear/46.9in (1,191mm)
Suspension: Telescopic forks front, dual shocks rear
Tires: 2.75 x 17in front and 3.00 x 17in rear
Brakes: 25mm SLS drum front and rear
Weight (dry): 185lb (84kg)
Fuel capacity: 2.25gal (8.5ltr)
Oil capacity: 1.4 quart 2-stroke oil tank
Price now: $1,200-$3,000

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“Think of the most challenging terrain you have ever tackled with a trail machine. Now take a good long look at the new Bridgestone TMX-7.” — Sales brochure by the U.S. importers, Rockford

Trace St. Germain works with the National Hot Rod Association as part of the Safety Safari, a group that performs the behind the scenes tasks at the track when the NHRA is racing. He is part of the fire crew who run out to get the racer away from the vehicle and extinguish the blaze when something catches on fire, a not-infrequent occurrence after a crash. He also competes on his own drag bike. Racers tend to band together, and affable Trace has made friends with many of the other drag racing competitors, mechanics and vendors. Four years ago, Doug, one of Trace’s drag racing friends, offered him a free motorcycle. “I’m not doing anything with it and I know you like to do restorations.” The motorcycle was this Bridgestone TMX, an uncommon model of an uncommon brand. Due to the scarcity of both information and parts, it took Trace four years to restore it.

Looking back

Although Bridgestone is not a name many motorcycle enthusiasts associate with motorcycles, in the 1950s and 1960s, Bridgestone made well regarded and technologically advanced 2-strokes. These bikes were exported to the U.S. and several other countries and did well in racing before the factory stopped motorcycle production around 1970.

Bridgestone was, like many other motorcycle companies, born from the ashes of World War II. The company started making tires in the 1930s. Its founder, Soichiro Ishibashi, decided to name his enterprise “Bridgestone,” a translation of his name into English. Inexpensive personal transport was a necessity after the war, and Bridgestone started looking into supplying this need. At first, the company built bicycles, but soon considered adding a power unit. The first tiny engines were supplied by Fuji Precision Engineering and bolted on sturdy bicycle frames. Small but real motorcycles were first built in 1958.

In 1954, a group of American entrepreneurs formed the Rockford company to import sewing machines from Japan and market them through Montgomery Wards. Shortly afterwards, Rockford began importing Mitsubishi-built Silver Pigeon scooters. Most of these were also sold through Montgomery Wards, but Rockford also started building its own dealer network. By 1962, scooter sales had declined, but Honda was doing well selling its Super Cub step-through. Looking to market a similar two-wheeler, Rockford approached Bridgestone, by then a major tire, motorcycle and bicycle manufacturer, and arranged an exclusive import arrangement for the Bridgestone motorcycle lineup.

Consolidation

The early Sixties saw a shakeout in the Japanese motorcycle industry. When Lilac and Tohatsu stopped building motorcycles, Bridgestone hired their engineers. The Tohatsu engineers had an in-depth knowledge of 2-stroke technology and applied their ideas to improving Bridgestone engines. Starting in 1964, Bridgestones featured disc valve engines and oil injection lubrication.

Disc valves, also known as rotary valves, look like a pie with a wedge taken out. They are set in a housing and keyed to the crankshaft. Disc valves allow the fuel/air mix from the carburetor to flow into the crankcase at the right time in the combustion cycle and prevent reverse flow back into the intake port during the compression stroke of 2-stroke engines. There have been some attempts to build 4-stroke disc valve engines, but none of the engines have gotten much past the prototype phase. Two stroke engines with disc valves have been used in many different applications, most recently on Rotax 2-stroke engines.

In 1965, Rockford persuaded Bridgestone to start building production race bikes. These small racers racked up wins in American off-road and flat-track racing, and one even won its class in Daytona. In 1966, Bridgestone formed a Grand Prix team, which did well in its two seasons of international racing. Bridgestone decided the team was too expensive and pulled out at the end of the 1967 season.

Changes ahead

In the late Sixties, Bridgestone was finding success selling its tires, motorcycles and bicycles: 240,000 motorcycles were produced in 1965. Success, however, was a mixed blessing. The plant that made both tires and motorcycles was running out of room. Some of Bridgestones’ best tire customers were other motorcycle manufacturers, who made it known that they were not pleased to be buying tires from a competitor. In addition, Bridgestone was aware that the U.S., its largest market, was considering clean air legislation that would severely impact 2-stroke engines.

Bridgestone decided to phase out motorcycle manufacture, which ended at some point between 1969 and 1971. Before the company did so, however, they brought out some new models, including the 99cc TMX, intended as a dual-sport machine. In the 1960s there were a lot more places to go off-road riding than there are now, and few young people had trucks to haul a dirt bike. As a result, many people wanted a street legal motorcycle that was capable in the dirt.

The TMX was first introduced in 1968 or 1969 — the timeline is uncertain. A 1968 TMX was advertised for sale recently. On the other hand, a 1970 brochure stated that the TMX was a new model. It featured a welded tubular steel frame with a built-in skid plate, relatively long suspension for the 1960s, a dual rear sprocket to allow easy gearing changes and a high exhaust. Advertising brochures boasted that the drum brakes were not only larger than necessary but also waterproof. The engine had a ball and roller bearing lower end, a chromed cylinder bore and oil injection lubrication. It made 11 horsepower and was good for a claimed 60mph. A back rack came with the bike. It is uncertain how many were made, but TMXs come up for sale from time to time.

There don’t seem to be any full magazine tests on the TMX. In 1969, Cycle World printed a one page impression of the bike, praising its ability to climb hills and put up with desert heat. “The little Bridgestone didn’t even wheeze under severe pounding.” Period magazine testers praised the smooth running, good handling and comfortable ride of other Bridgestone models, and tried and failed to like the quirky gearbox. 100cc Bridgestones have four speeds down. Neutral is at the bottom of the shift pattern, followed by first again. It is possible to forget what gear you are in and shift directly from fourth to first. As one Australian magazine said, “There are easier ways to leave big black marks on the asphalt!”

Bridgestones today

It is now over 50 years since production ceased, but parts availability is remarkably good, considering that Bridgestones were never top sellers. There are several online clubs devoted to Bridgestones, and information can be found — it just takes a fair amount of work. A good percentage of the four years before the restoration of this TMX was complete was taken up in research on the machine. Luckily, the 350cc Bridgestone is a popular vintage racer, which keeps the websites humming and the parts sellers in business.

The friend who gave this bike to Trace bought it new from a store that made a lot of its money selling chain saws. Doug, the friend, had previously bought one of the 90cc Bridgestones, and Doug’s brother really liked that bike. When the TMX came out, Doug decided to buy it — the TMX had two more horsepower — and give the 90cc bike to Brother. At the time, there were a lot of dirt roads in the area (most now paved over) and Doug spent his spare time trail riding. When Trace got the bike, the odometer showed something over 5,000 miles. Doug could pull wheelies with the chain on the larger sprocket. A conscientious owner, Doug always cleaned the TMX after an outing and stored it inside. As time passed, however, Doug got involved in other pursuits, and the bike sat for longer and longer periods of time.

Trace started researching the TMX and quickly found out how rare it was. “I was lucky — everything was there, except the rear fender. The fender had been chopped off.” Doug also had lots of extra parts, which went to Trace along with the bike. When he was actively riding the bike, Doug kept wearing out the cush drive in the rear wheel, and decided to buy some extra sets. Trace’s haul included three cush drive sets in perfect condition.

Getting started

Trace approaches restorations in a very organized way. He starts by doing research, so he knows what the bike should look like when he is finished. The next step is stripping the machine, carefully storing the parts so he knows which bolt goes where, and making lists of what needs to be painted, what needs to be chromed and what needs to be replaced.

One of the best sources for Bridgestone parts, information and help is Richard Clark’s website. The website has downloadable manuals, articles and period brochures. Clark sells NOS parts and will provide help to owners via email. He had a complete taillight assembly, which is now installed on this TMX. Other parts were located on that sure fire parts supplier, eBay, including a complete rear fender. The fender had a few dents, but resourceful Trace bought bodywork tools at Harbor Freight and started gently tapping. “The dents took me two weeks to hammer out.” Luckily, although the tank and side covers needed paint and chrome, they were dent-free. The rack was damaged, but repairable.

A problem with rare motorcycles is matching the paint. Paint chips are generally unavailable, and the restorer hopes that an un-faded spot of paint can be found. The taillight assembly was doubly valuable: not only was it a needed part, but it also had the silver paint that Trace needed to copy for a match on other parts. The badge on the side cover covered a spot of blue large enough for the painter to reproduce.

The cylinder head was in good shape, but for some reason was drilled for an aftermarket compression release. Trace was able to locate a good head, again on eBay. The piston was very usable. He had the cases vapor blasted, which cleans everything up without leaving sandy residue or damaging small parts. Trace’s goal was to replace all exterior bad parts with new old stock, and he succeeded except for one Honda cable.

A lot of Japanese motorcycle frames of this era have splatter around the welds, but Bridgestone’s quality engineering extended to the welding. Trace was impressed by the clean and good welds. Since the original paint was rough, Trace had the frame painted with epoxy paint, which provides a finish that is very close to the original.

That major restorer bugaboo, the exhaust system, was rusty and pitted, as it often is, but had no dents. The chrome shop Trace uses was able to make the header and muffler look new. The shop also refinished the wheel rims. Bridgestone Motorcycle Parts had packages of NOS spokes, but some of the spokes in each set were rusty. Richard, the owner of the website, solved the problem by sending Trace four sets of spokes, two for each wheel. There were enough good spokes in the double sets to make up a front and rear wheel.

The restoration was finally chugging along nicely, but two things happened to put it on hold: Trace got involved in a home remodeling project that consumed all of his time for several months, and the countershaft sprocket on the bike was not usable. A NOS sprocket could not be located after a months-long search. Finally, Trace contacted Sprocket Specialists a company that makes custom sprockets for race bikes and also sell ready-made sprockets. Trace has been using them for years for sprockets for his drag racer. Sprocket Specialists matched the specs to a Honda sprocket they had in stock.

The bike was done 10 days before the big Antique Motorcycle Association show in Dixon, California. Trace’s attention to detail was rewarded with over 95 points out of 100. He then took the TMX to the Hillsborough show and won his class. Figuring it would make a reasonably decent pit bike, Trace took the TMX with him to a drag racing meet.

Doug, the former owner, showed up at the meet, rode past Trace’s pit — and didn’t see the TMX. He came over to Trace’s pit to say hi — and didn’t see the bike. Finally, Trace pointed it out to him. “Doug nearly fell over.” MC