2024 Collector’s Corner Guest: Yoshimura R&D of America There are brands that need no introduction, and in the world of motorcycle performance several names fall in this category and YOSHIMURA is arguably one of them.
Their iconic logo in Japanese characters is not in any need of translation to all of us who grew up in the seventies. Their performance engine products became “must have components” for racing tuners and the term “Yoshi Pipes” was synonymous with performance exhaust systems, not only in Japan and in the USA, but all over the world.
According to their website, its founder, Hideo Yoshimura, an aviation engineer, opened a little bike shop in 1954 by renting a corner of the family business’ ironworks and named it Yoshimura Motors. His shop was soon filled with the happy sounds of motorcycle engines. They were the “birth cry of Yoshimura”.
Eventually, Hideo was known around the racing circles by his peers as “Pop” or “Pops”, an affectionate way of addressing a man old enough to be their father. He was invited by the American troops to participate in motorcycle drag races at the Itazuke Air Force Base where he entered his BSA Golden Flash. His reputation as a tuner grew with every victory at the track.
Eventually he started developing and selling camshafts, valves and porting cylinder heads for competition. After several years of success Pop decided to move from Kyushu to Tokyo in 1965 where there were better business opportunities. His new shop bore the English inscription YOSHIMURA COMPETITION MOTORS and the now famous logo was introduced.
In 1965, Pop was asked by Fumito Sakai (Yaesu Publishing president) to contribute to his Motorcyclist magazine. His monthly articles ran from February to April 1965 (on motorcycle tuning), and then from April to August 1967 (on 4-stroke engine tuning).
Pop’s track-proven, detailed 4-stroke engine tuning tips ranged from carburetor selection to cylinder head modification, which involved valve timing adjustments and high-lift camshaft design and fabrication. All of this helped make Yoshimura a national brand.
The series of articles was the first of its kind in Japan, and was well received by many, including the Honda engineers who built the CB72/77. Even to this day his original writing is regarded as a bible among enthusiasts.
“Since Pop had moved from Zasshonokuma, Fukuoka to Fussa, Tokyo, demand for the engine tuning and modification, not just of motorcycles such as CB72/77 but also of cars, was growing exponentially.
One of the most popular cars to tune and modify back then was the Honda S600 and S800 sports cars which were equipped with race-bred twin-cam 4-cylinder engines”, the website’s story explains.
Pop’s results in car racing were equally impressive. By then, his son Fujio and his daughter Namiko had already joined the firm.
Namiko had been playing a significant part in the family business – from procurement to administration – as her father’s right hand since they moved to Tokyo.
The website’s story continues: “Another idea was the high performance 4- into-1 exhaust system for race cars, which later revealed to be an invention.
The idea came out when Pop was trying to install a S800 engine on a Brabham BT15 Formula 3 chassis at the request of racing driver Isamu Kasuya (a legend Formula Libre 500 driver and the winner of 1969 Fuji300 km Golden Formula).
While working on its exhaust configuration, the four separate exhaust pipes were tentatively welded into a collector in order to reduce weight and for better appearance. The result was surprising, as the newly-devised exhaust system led to a dramatic increase in engine power and mid-range torque, making the Brabham-Honda S800 faster than Toyota 2000GT”.
The world’s first 4-into-1 motorcycle exhaust system made its debut at the Ontario 250 in October 1971, at the Ontario Motor Speedway, a race track in the outskirts of Los Angeles, California. The Yoshimura-tuned engine of the Krause Honda CB750 was ridden by Gary Fisher and Fujio came to the US to support the effort.
The results of the races, however, were not what they expected. “’For the 1972 Daytona 200, Krause Honda again entered two CB750’s, ridden by Gary Fisher and Roger Reiman. The race was on March 12. As Pop arrived at the Daytona International Speedway, he was greeted by a peculiar sight. The 4-into-1 exhaust pipe became so popular among competitors that it was everywhere on the track. Most of them were fabricated by small tuning shops. It was phenomenal.
Pop was fascinated by how Americans reacted to the new concept which, in contrast, had been rejected by Japanese engineers. What provoked the American interest in 4-into-1 was perhaps not some logical reasoning, but the sound it produced”, the website continues.
The very first opening round of the AMA Superbike Championship series at Daytona International Speedway was monopolized by three BMW R90Ss. They were all tuned by American BMW importer Butler & Smith. Steve McLaughlin (R90S with twin rear shocks) won the race in a photo-finish over Reg Pridmore (R90S with a rear monoshock).
But another sensation of the race was Wes Cooley riding a Yoshimura Kawasaki Z1, who started from the last row of the grid but managed to finish 4th. The bike was tuned by Pop himself at Yoshimura R&D of America, which he established in North Hollywood, California on June 1, 1975.
After campaigning Kawasaki Z1s, Pop showed interest in a new 750 cc engine from the company that would be a partner of Yoshimura for the next 40+ years: Suzuki.
That partnership between Yoshimura and Suzuki began in August 1976 when Pop met Suzuki engineer Etsuo Yokouchi, Director of Suzuki’s Motorcycle Design Department.
The Yoshimura Suzuki GS750/944 made its AMA Superbike debut with a victory on September 11 in Round 6 at the Laguna Seca Raceway in the hands of Steve McLaughlin.
And the rest, as the saying goes, is history.
We recommend reading the fascinating 20-part story of Yoshimura in their website, from its beginnings to the present, which includes ‘’behind the scene”’ situations, both family and business related. It is honestly worthy of a movie plot. The story, written by Tomoya Ishibashi, is illustrated with numerous historic photographs. And, as we said, fascinating.
We welcome YOSHIMURA R&D America to our Collector’s Corner.
Hector Cademartori
(Photos Courtesy Yoshimura R&D America)
