1972 Honda RC125M
1972 Honda RC125M
The 1972 Honda RC125M. The earliest works Honda motocross bike in existence and it is all original. No its not a pre-production Elsinore, its a full works RC Honda.
Honda Motocross - The Beginning
When the 10 boxes containing the 1972 RC125M arrived from Japan, I was very eager to see exactly what this bike was all about. Prior to this, the only time I had seen or ever heard of a 1972 RC125 was back in 1972. The bike was featured in a small press release in Cycle World magazine. It looked super trick and competitive but that was it. It never showed up anywhere and for nearly 40 years the details remained unknown and forgotten. The truth is, very few were ever made and they never left Japan. The bike featured here is the only one left in the world and it is in 100% original condition. It is the earliest known RC Honda motocross bike in existence.
When I started to open the boxes, Not only was the bike in remarkable condition, I was stunned by the quality of the individual parts and how lightweight everything was; this is a very special bike. The attention to detail rivals that of the 1980’s HRC bikes and in many ways surpasses them. The quality and handwork is amazing and many of the parts are like jewelry. Parts like the titanium exhaust manifold, needle bearings in the clutch cover for the kick-start shaft and the clutch assembly just to name a few. Everything in the engine is machined with laser like precision. You spin something and it just keeps spinning, no friction. I had never seen anything like this and the weight at 138 lbs. is just mind-boggling! I have seen inside Bob Hannah’s championship bikes. I have seen inside DeCoster’s and Joel Robert’s Suzuki’s. The HRC Honda’s…. seen them too. All unbelievable bikes but this was way over the top. I had to find out what the story was behind this incredible motorcycle. Fortunately Holly, the guy I acquired it from knows and is very good friends with the guy that actually developed and raced this very motorcycle in the “All Japan Motocross Championship” back in 1972. Mr. Taichi Yoshimura. After asking about the history, Taichi was kind enough to sit down with Holly and his wife Masayo and tell the incredible back-story from the beginning. This would be the first time this story would be told and in print anywhere! To fully understand the history and significance of this historic motorcycle a little background history is warranted.
Taichi Yoshimura tells the story in its intirety for the very first time to Holly as Holly's wife Masayo takes notes. This is real history folks.
1972 Honda RC125M Photos
Honda Motocross History
From the inception of the sport thru the early 1960’s, motocross was dominated by 4-strokes. From the late 1950’s thru the early 1960’s, companies such as Monark, Lito, Husqvarna, FN, BSA and others made some awesome well-developed motocross machinery. These bikes were designed and for the most part hand built by some of the best engineers, craftsmen and riders of the day. Their ability to travel at high rates of speed over extremely rough terrain was truly amazing. They were state of the art motocross bikes made in very limited numbers and ridden by the best motocross riders in the world to do one thing, win championships. But all of that was about to change. By the early to mid 1960’s, European manufacturers like CZ, Husqvarna and Greeves to name a few, started designing and building 2-stroke motocross bikes. These bikes were lighter and handled much better than the 4-stroke bikes that had dominated the sport for decades. Almost overnight the 4-stroke motocross bike became obsolete.
It’s no secret that in the late 60’s and early 70’s, motocross had become the fastest growing motorsport in the world. It’s also no secret that at the same time, the Japanese companies Suzuki, Yamaha and Kawasaki were getting involved in a big way and by the early 70’s were dominating the sport at the professional level with super lightweight 2-stroke works bikes. This dominance led to unprecedented sales of their production bikes and to this day, the sales figures from this era remain unmatched! People from all walks of life were now getting involved in this new phenomenon of motocross.
1967 was the year that motocross officially came to Japan. It was the year of the first “All Japan Motocross” championship, sanctioned by the Motorcycle Federation of Japan. At this time Suzuki led the way with a development program that started in 1965 and was well on their way to building a competitive 2-stroke motocross bike. By 1970 Suzuki had developed the incredible works RH70 and in the hands of multi world champion, Belgium’s Joel Robert, delivered Suzuki and Japan’s first FIM World Championship. Yamaha wasn’t far behind with Sweden’s multi world champion Torsten Hallman and Kawasaki was now involved too. Honda however, was not involved. In-fact, Honda’s founder and President Mr. Soichiro Honda went out of his way to say “Honda will never build a 2-stroke motorcycle!”
Mr. Honda was a very competitive man and under his supervision, Honda Motors was very much involved in GP road racing. His attitude and approach was much the same as Enzo Ferrari’s of auto racing fame, “win at all cost.” Second place was not an option and everyone on the team understood this. He hired the best engineers and technicians that graduated from the most prestigious universities in the world to design build the best race bikes ever built. Some amazing machinery was conceived and built by this early Honda Motors works R&D team like the RC166 250cc six-cylinder 19,000rpm road-racer or the 5 cylinder 125cc. These bikes were 4-strokes! The result of all this was complete dominance in the super competitive, highly prestigious world championship road race series in Europe. The cost of this was staggering but Honda achieved a global status that no ad-campaign could buy. They proved to the world that they could design and build anything better that anyone else. When they achieved all their goals, they stopped and after the 1967 season, Honda pulled out of GP road-racing.
Now that Honda had pulled out of GP road racing, at about the same time motocross started in Japan, some of the younger engineers in the works R&D team formed a voluntary group called “The Association to Study the Motorcycle.” This was an independent group, not officially an arm of Honda, even though they all worked for Honda. These guys were race enthusiasts through and through and collectively, they turned their eye and attention to this new sport of motocross.
Since it was common knowledge throughout Honda Motors that the president disliked 2-strokes they were limited to using a 4-stroke Honda machine in an attempt to make it competitive against the 2-stroke machines from other manufacturers. The bike they chose to start with was the Honda production SL125. After spending considerable time reducing its weight and modifying the engine they felt they were ready to put their highly modified SL to the test. In May of 1969, as Honda’s first official motocross team, they entered the 6th round of the MFJ Motocross Grand Prix in Kurume, Fukuoka Japan.
In their first real competition in a sanctioned race against the best 2-stroke works machines from the other Japanese manufacturers, the sobering reality set in. Although they finished the race, Honda’s highly modified 4-stroke was easily outclassed and their attempt ended in failure. They were made acutely aware of the progress of the state of the art 2-stroke engines and that any attempt to win with the 4-stroke would be very difficult. They also realized that the more motocross pervaded as a sport, the more Honda would be left behind as long as they hesitated to build a 2-stroke engine.
The atmosphere within the company was still very strong against the 2-strokes but the Honda race team did make the company aware of the situation and understand the problem. This however did not dampen their enthusiasm. At a request made by the younger engineers to R&D management, they were allowed to purchase two European motocross bikes for evaluation. This was a private and unofficial arrangement made by the R&D management and the independent voluntary group. One bike was a Greeves and the other a Husqvarna. When the bikes arrived, the young engineers examined the cutting edge machines in great detail and often dreamt of the day when they could surpass them.
Development of project 335
At Honda, development of a new 4-stroke machine was underway. It would be the successor to the “CL” scrambler series. It was the 250 single SL250. Many of the members from the R&D Team gave it a very careful consideration as the foundation of a race bike but considering it would have to compete against 2-strokes they couldn’t help having misgivings about its potential. The rest of the bike seemed good and so they decided to submit a proposal for developing a 2-stroke engine for the SL250T, as it would be called (code name 335). This would run parallel with the original plan of the development of the 4-stroke engine. The proposal was submitted in January of 1971. R&D management allowed this to happen mainly because of the enthusiasm of the young engineers. It cannot be stressed enough how taboo the idea was for Honda to build a 2-stroke at this time.
When the SL250 4-stroke development was completed it was a huge success as an off-road bike and the 2-stroke project quickly lost its importance. The new 4-stroke single was in some ways a break through, but it still was not up to par with the 2-stroke race engines at any level as far as performance went.
Even though the project was shelved, the young engineers proceeded to develop the new engine and at this time the code name was changed to 335B. Within 6 months they had the engine power level clearing 30ps/7000rpm. This was their tentative goal.
With this goal achieved, they started on the chassis. At first the frame was copied from a Husqvarna. Then the remaining components were from other various competitors. The final bike looked like some sort of homemade bike patched together but this was of unimportance to the enthusiastic engineers. They wanted to test the engine in a real life motocross environment in a real race and they wanted the results as soon as possible. In a strange way, this was the very first 2-stroke Honda motocross bike.
Once the bike was completed they decided to enter it in the All Japan Motocross Championship. Since this was not an official Honda, they chose a race in the series that was far away from any large city where the crowd would be smaller and hoped that they wouldn’t draw any attention. They entered the race as a private team. The event was held August 22, 1971 at the 9th round in Mine, Yamaguchi. Contrary to their expectations, they were recognized immediately and got all kinds of attention from the other teams and the media. They DNF’d their debut race due to suspension problems and not enough preparation to a hastily built machine but they were able to get enough feedback on the engine performance. Most of it was positive. The magazines and other media outlets wasted no time in reporting about Honda’s new 2-stroke at Mine, Yamaguchi. The horse was out of the barn!
Honda's first unofficial 2-stroke motocross bike enters its first race on August 22, 1971
Much attention and interest was now directed at Honda and this new 2-stroke motocross bike. The trouble was it wasn’t an official Honda project. It was just some enthusiastic Honda engineers from the private club, “The Association to Study the Motorcycle.” What would happen if Mr. Honda found out? After all he hated 2-strokes and publically said the company would never build one. Now that the secret was no longer a secret the R&D management decided that the 335B project idea was successful and due to the enormous interest from the media, they decided to make an official proposal to Mr. Soichiro Honda himself. They were going to do the unthinkable. Ask Mr. Honda, the same guy who said Honda will never build a 2-stroke, to build an official Honda 2-stroke works motocross bike.
It’s official Honda enters motocross with a 2-stroke
Those that were at the meeting remember it well. After quietly listening to the proposal, Mr. Honda’s response was very short and to the point. “If you insist on building a 2-stroke engine, you can do it.” Once you start, it had better be the best 2-stroke bike in the world and the engine should be superior to any of the competitors!” The young engineers dream had come true, they got the green light, but the pressure was on. Mr. Honda was a very driven man especially when it came to racing. He did not accept losing or failure and did not handle it well when it happened. Some of the best engineers in the company learned this the hard way. You did not want to be on his bad side if you were part of something that did not work or win. This coupled with the fact that he did not like 2-strokes really put the heat on these young enthusiastic engineers. They absolutely could not fail. They had to dominate like they did in the road-race GP’s and build the best motocross bike in the world. To this day, no one knows if Mr. Honda ever knew about the secret Honda 2-stroke 335B.
Once the President gave the OK, the project was renamed 335C. The same R&D engineers that built the incredible works road-racers that dominated the GP’s in the 60’s would now start with a clean sheet of paper and attempt to build the best 2-stroke motocross bike in the world from the ground up. Nothing would be spared in this attempt. They had to succeed!
“This was a huge deal,” says ex-Team Honda racing manager and current Honda R&D employee Dave Arnold, who helped build Team Honda into the biggest, baddest and most successful motocross team ever during the ’70s and ’80s. “Mr. Honda was absolutely a win-at-all-cost sort of guy, and he was also a little crazy – so I’m positive the team was very, very nervous about going to him with the idea. Mr. Honda’s temper was well known throughout the company, and there were several incidents where he publically abused engineers emotionally and physically for mechanical failures.” "Mr. Honda did not like 2-strokes, that’s for sure. But he was also no dummy, and he obviously realized where things were going. And since Honda was first and foremost an engine company, it made sense for him to want to dominate, and right out of the gate. It was all about proving Honda was the best engine manufacturer in the world – just as they had so successfully in the ’60s during their GP roadracing experience.”
As far as putting together a race team for the AJMC, Honda already had the pieces in place. They had an excellent administrative staff such as manager, mechanics, engineers and coordinator with plenty of professional race experience. Kunihiko Aika was the chief engineer. Katsumasa Suzuki was the chief mechanic and Kazuhisa Sekiguchi was the MX team advisor. In November 1971 the negotiation of two of the best riders in Japan were being pursued in profound secrecy. They hired Koichi Ueno, and from the works Suzuki team, Taichi Yoshimura to be the development riders and compete in the AJMC. The announcement of this caused a huge sensation in Japan and immediately put the duo in the limelight. Shortly after the development started, Ueno developed an illness that would keep him bedridden the remainder of the season and this left Yoshimura alone to develop and race the bikes.
In January 1972, the official name RC250M was given to the 335C. This was the official name for any machine developed under “Honda Works.” If is designated RC it is works and that means this will be Hondas best effort for performance.
Design, developing and testing began very soon and the work was very intense and focused. The bike was getting better and better at a very quick pace. The bike had progressed to the point where the team felt it was time to enter it in the AJMC. The opening round was March 12, 1972 at a high-speed track in Yatabe, Ibaragi. In the bikes debut race, the result was a 6th place. The RC250M had a few setbacks such as an over heated engine, carburetor jetting was off and wrong suspension setting. The team’s inexperience in motocross was evident as this was completely different than road racing. Catching up to the other teams experience and surpassing them was a priority.
After the first race the team worked on all the issues one by one. Trial and error until it was perfected. “We want to catch the front runners and somehow overtake them no matter what. We want to gain the top technology in the 2-stroke world.” It was those days that such enthusiasm gave them energy to carry out the unique research at the racetrack. For example; One of the team members went up to a competitors works machines from behind, and pushed the palm of his hand onto the exhaust pipe so that the mark could be measured to learn it’s diameter that had a big influence of engine power. Another member stayed at the track late and after everybody left, went through the other works teams trash to try and find anything such as a broken piston ring or gasket so they could analyze the material. After a great deal of trial and error, the team felt the RC250M was ready to win.
The first motocross victory
On June 4th 1972, round 6 of the AJMC at Kannabe ski area, his Highness Prince Takamatsu of the Imperial Family of Japan and founder and president of Honda Motor Company Soichiro Honda were in attendance in the honored visitor’s gallery. They were there to see the first official 2-stroke works Honda compete for the championship. The team was extremely nervous because of his presence. It was just eight Months before that Mr. Honda approved the 2-stroke and everyone there was fully aware of Mr. Honda’s words. The bike had to be the best in the world.
In the first heat after getting the holeshot, Taichi was in a close battle for the lead and ended up with a 2nd. It was his best moto finish of the season so far. In the second heat, Taichi used the fantastic Honda power, got the holeshot again and went wire to wire for the win. Winning in front of Mr. Honda was a great satisfaction and the team that worked so hard had finally won. The research team and their RC250M had taken an important step into making the best 2-stroke engine in the world.
History is made as the Japanese crowd mobs Taichi in celebrating Honda's first ever motocross victory. Mr. Soichiro Honda himself was present that day.
Payday! All the hard work of the entire factory Honda team has finally paid off.
No comment necessary.
Taichi on the podium being congratulated as Yamaha factory rider Hideaki Suzuki (left) looks on.
The 1972 RC125M
Once the development on the RC250M was complete, it was decided to put the same effort into developing a 125, the RC125M. This was started in 1972 and much of what was learned developing the RC250M was applied to the RC125M. And because of this the development proceeded at a much faster pace. When completed the bike was extremely fast and very lightweight. The new RC125M competed in its first race on July 2nd at the 7th round of the AJMC and finished a very respectable 4th. In the 8th round, they moved up and got 3rd. In the 9th round, Taichi Yoshimura and the RC125M won! This was Honda’s first ever win in 125 motocross and it was only the third time the bike had ever been raced. An amazing achievement since they were competing against the works Yamaha’s, Suzuki’s and Kawasaki’s, all of which had many years of experience and very good bikes.
The 1972 RC125M was the result of two years of solid non-stop development. Even though construction of the bike started in 1972, much of the data that the research team learned from the 335/RC250M project was applied to the 125. The bike was excellent almost from the beginning. Here at an "All Japan Championship" race, a competitor checks out Taichi Yoshimura's exotic 138 lb. RC125M's. Notice all the Honda engineers in the background. These guys were serious.
A 125 is much more sensitive to weight and power than say a 250. Nowhere is lightweight more important than on a 125. To produce low lap times, the bikes momentum on the race track is very important and must be maintained. A 125 simply does not have the engine torque to pull itself out if any lost momentum like that of a larger bike. The Honda engineers understood this and to build the best 125 possible, weight reduction was a primary goal. Each part was designed and made as light as possible without sacrificing reliability. Parts like the swingarm, wheel hubs and suspension components that make up the un-sprung weight were given much attention to be very lightweight. At just over 3 lbs, the all aluminum swingarm is a great example of how much attention was paid to weight reduction. The rear shocks were made with extra large bodies and large shafts but were very lightweight. Since the RC was made to be raced and serviced by Honda’s works team only, extreme measures could be taken in reducing weight as cost was not an issue and the bike was maintained by some of the best engineers and mechanics in the world.
Honda has always had pride in their engine development and the RC125M was no exception. The engineers applied every bit of knowledge from their master’s degrees in engineering and then some when designing the little 125 power plant. Several engine designs were initially tried with different configurations. Five and six speed gearboxes were used and the ratios were very carefully matched to the engine power band. Only 350cc of oil capacity was used in the transmission case. The engine components were made with the lightest and strongest materials possible. They were machined with extreme precision at very close tolerances. This greatly reduced any friction of moving parts. The entire clutch assembly was fastened to the main shaft with a large cir-clip to save weight. The complete engine weighed less than 30lbs and made 21 horsepower peaking at 9500rpm.
Overall the bike was a huge success. With a very lightweight chassis and a very highly tuned engine the acceleration of the RC was overwhelming compared to anything else in its class. Also aiding acceleration was the increased traction found as a result of the light weight. Roger DeCoster noticed this atribute with the super light-weight works Suzuki's. The extreme lightweight of the machine was also a huge advantage on the rough tracks as the bike could easily stay on top of the whoops gaining valuable time. Rider fatigue was greatly reduced. Handling was also improved as the rider could literally place the bike just about anywhere on the track at will because of the extreme light weight. Braking was also improved. In fact, every single aspect of the bikes performance was greatly enhanced because of the super light weight.
The result of producing a bike of this caliber is an incredible achievement especially since it was Honda’s first effort at a 125 2-stroke. For a 125 to be over 60 lbs lighter than a standard 125 of the day and carry an engine that has near 250 performance puts this bike on the short list of one of the most advanced motocross bike ever built in relative terms. The young engineers in Honda’s works R&D shop that started out as a group of enthusiasts with a dream succeeded in building a bike that I’m sure surpassed even their highest expectations. But when Soichiro Honda is your boss and says it had to be the best 2-stroke in the world, they really didn’t have much of a choice.
Taichi Yoshimura really hauling during a AJMC championship race on the feather weight RC125M. After Koichi Ueno became ill, Taichi ended up being the sole Honda team rider for 1972.
Taichi's Yoshimura's 1972 RC125M as it sits today. This is the only example left in the world and we are very proud to have this priceless motorcycle in our collection.
A photo CD containing over 200 high quality photos and a video of the bike in action is available in the MXWorksBike.com Store or on ebay, click the logo.
See Taichi Yoshimura ride a 1972 Honda RC250M (Honda 335c) replica for the first time in 42 years in our events section or by clicking HERE
Taichi Yoshimura Reflects
At the end of the 1971 season I received an offer from Honda to develop and race their new 2-stroke motocross bike. I knew of Honda’s high standards and thought they would do a good job so I decided to accept the offer. Prior to this I was a factory rider for Suzuki.
When I saw the bike for the first time Mr. Matuura and Mr. Kihara was riding it at the Nishinihon Circuit. At the time I never heard or thought Honda would make a 2-stroke. I thought the bike would be successful though because Honda was involved.
When I first rode the bike the instantaneous power of the engine was much more powerful than I was expecting. There were some durability problems though in the beginning, mainly overheating.
One of the problems we had initially was to learn the correct silicone content for the piston. For example; originally the material of the piston was made on the basis of our 4-stroke pistons that are always soaked in oil. The tolerances were not as critical on a 4-stroke machine because of this. On the 2-stroke, the cylinder had portholes and because of the portholes the cylinder temperature was not consistent with the temperature of the piston. This was compensated for by the silicone content of the piston. We had many engine failures because of this in the beginning. All of this was new to Honda because prior to this, they only built 4-strokes. Cylinder studs that went from the case to the head also contributed to engine failure. The stud gets very hot but has no way to dissipate the heat and will cause the cylinder to distort. We solved this by fastening the cylinder to the case near the transfer port. We had to learn all of this through a continuation of trial and errors.
We had a lot of knowledge of 4-strokes but knew very little about 2-strokes when we first started. I gradually understood the importance of the exhaust chamber. It was similar to the camshaft of a 4-stroke. Gradually we became accustomed to the 2-strokes, but they were very noisy! Also, in the beginning the suspension was not so good. By the time the 1972 race season began, we had the engine very reliable and the bike was ready.
I was very confident and thought if the bike didn’t break down I could win. When I won with the 250 and the 125 for the first time, both races were rainy days and the bike was not as big of a factor as it would have been in dry conditions. The 250 win was at Kannabe and the 125 win was at Aso. These were the first wins for Honda for the 125 and 250.
In those days technology was not like it is today. Back then, If the bike didn’t fit the rider you would lose. When the rider is in agreement with the bike the gears mesh and you get good results. I was a technical rider and very confident in my ability, this was good for development. We did some mean things to the young engineers back then. I remember sometimes kicking the machine when they didn’t get it right. They must have been upset with me at times and when I look back on it now, I was sorry for kicking the machine that many people made for me. However, these days there are many young people who could use a good kicking.
I enjoyed my time at Honda very much. I liked developing a new bike more than I liked racing a developed one. Honda gave me a spot that I really enjoyed. It was a pleasure to work there developing the RC works bikes. While developing the bikes, I could feel the difference in performance of the machine little by little until it was right. Honda is superb at development in an unknown field.
The first races I won with the RC will always be in my memories. But I don’t forget about the races I rode with determination even if I won or lost.
Taichi signing the number plates for our 1972 RC125M, the sand cast queen!
We are so grateful to Mr. Taichi Yoshimura and our friend Mr. Holly for making all of this possible!
Summary of the RC125M
Way back in 1972 when I first saw the press release in Cycle World featuring the RC125M, I remember being much more impressed with it than I was with the 250 (335) bike that was announced a little earlier. The top production 125 bikes at that time were the 200+ lb. Penton’s and Monark’s. In comparison, the Honda RC was in another world. It was very sleek and had that all business “no frills works bike” look to it. Everything just seemed like it was in the right place. Probably the most impressive part that stood out in the press release was the stat sheet. They had a claimed weight of 154 lbs. listed. This was unbelievable! It also showed how serious and to what level Honda was getting into motocross. From that point on, the 1972 RC125M has always been my favorite Honda even though the closest I ever got to one was that photograph in Cycle World magazine.
After close examination, the bike has far exceeded any pre-conceived expectations. The thirty eight year old mystery is now a reality. There are so many things that set this bike apart from the other works bikes but the thing that amazes me the most is the same thing that amazed me the most back in 1972. The weight, only it is 16 lbs lighter than the stat sheet said it was. I am a firm believer that when Honda wants to win, “get out of the way.”
These guys are crazy!
The official "Peter Rabbit" weigh-in, 63kgs or 138lbs.
Taichi Yoshimura Today
So what does Taichi Yoshimura do today? Taichi is as busy as ever. He owns the famous RS Taichi clothing company. An international high end motorcycle apparel company www.rs-taichi.com Also Taichi is still very active in motocross. He is the team manager for the Suzuki factory motocross team in Japan.