1971 Yamaha YZ250

1971 Yamaha YZ637

Torsten Hallman's 1971 YZ637 prototype Yamaha. Other than respraying the frame and engine cases, the bike is 100% original as Torsten last raced it.

  Torsten Hallman received this bike in the spring of 1971. He had just signed a three year contract to develop Yamaha's GP motocross bikes. At the time Suzuki was the only Japanese manufacturer competing in the world championships and they were dominating with Joel Robert and Sylvain Geboers going one, two in 1970. The YZ637 seen here was Yamaha's first effort at developing a world class performing GP motocross bike and early every part on the bike is hand built with weight being of most importance as it weighs only 185lbs.Torsten, riding this very bike scored Yamaha's first ever points in a GP with a sixth place finish at the 1971 Dutch Grand-prix. Yamaha being very serious cooperated with Torsten fully at every level and by the end of the season the bike was developed into a very competitive GP contender. This success led to a full GP effort for 1972 and then to Yamaha's first world championship in 1973 (the 1973 WC bike is also in this collection). The Hallman YZ637 is currently in it's original condition after its last race, the 1971 Swedish grand-prix.

In 2005 Torsten stopped by to visit and see the bike again that he spent so much time with back in 1971. He was kind enough to sit down with us and tell the story of how it all happened right from the beginning. I have to say that sitting down in the midst of all the historical works bikes, tape recorder on and listening to Torsten Hallman himself tell the story was overwhelming to say the least. We are so grateful to own the bike now and to be able to preserve it and the story for the ages. Enjoy Torsten's story below.

1971 Yamaha YZ250 Photos


Torsten Hallman's comments:

  At the end of 1970, after riding for Husqvarna for many years, I did not get any offer at all to renew my contract with them. I had won the world championship four times riding a Husky, and I felt I had a few more years left to race. I felt I was worth something but they didn't contact me at all. I felt really bad that I did not get any offer so I was completely on my own. There was a big race in Stockholm that winter and everybody was there with their new factory bikes. In those days we used to race motocross in the winter with studs in the tires. I was a Husky dealer at the time, so I took a brand new “400 Cross” off the showroom floor, entered the race and won! I beat everybody. I was once again the talk of the town. After that race, the news papers wrote, "He's not washed up yet." So here I was, still competitive and no factory support. I didn't know what to do.

   Suzuki had already come into motocross and Joel Robert had just delivered them their first world championship in 1970. Prior to this Suzuki had already tried to hire me in 1966 two years before they hired Olle Petersson. At that time, I turned them down because of my loyalty to Husqvarna. I decided now, that I would go to Yamaha. I spent a lot of time preparing a booklet showing my credentials, a marketing plan and a basic description as to why they should be involved. After Suzuki's recent success, it would only be natural for Yamaha to get involved. I got in my car and drove 1,600km down to the Yamaha headquarters in Amsterdam to meet the head boss Mr. Kuratomo. Yamaha was new to Europe and there were only six people working there, it was a very small operation. I met with Mr. Kuratomo and presented my proposal outlining all my ideas. I soon realized, he didn't even know what motocross was! He told me we will give you a DTMX and $300.00 per month to evaluate the machine. I was very surprised at his response, but I told him thanks but no thanks. After that meeting I thought they were not interested.

   After I went back home, I made it known in the motocross community that I had visited Yamaha. Word traveled very fast about the Yamaha visit. Even the US Husky importer Edison Dye heard about it. When Edison heard, he immediately contacted the Husky factory and voiced his displeasure about it. Edison was relying on my name and my participation in the inter-am series to promote Husky sales in the US. (Editors note: we have acquired the original two page letter Husqvarna wrote to Edison Dye. Click for  page 1 and page 2). About ten days after the Yamaha meeting, the Husky factory contacted me and arranged a meeting. When I met with them, they told me they had a plan where I would be getting a salary, bikes and spending about six months in the US promoting bike sales. Since I was married and had a daughter, spending six months away from home was a big commitment. I told them I would talk this over with my wife and get back to them.

   Two days after the Husky meeting, I got a call from Kuratomo. "I need to see you tomorrow" he said. The next day Kuratomo flew up to Stockholm and we met at the Palace hotel. He had brought with him a prepared three-year contract. It was everything I had hoped for. I was to get a good salary and develop the bikes. I didn't even talk to my wife about it. I signed immediately, even if I had to spend a lot of time in Japan and other places!  I was surprised by Mr. Kuratomos change in attitude towards me at this meeting and his eagerness to get me to sign the contract. I asked him "What has changed since we last saw each other in Amsterdam?" He told me how he made two copies of my booklet on how I wanted Yamaha to enter the motocross market. He sent one to Yamaha in Japan and the other to Yamaha in the US. The Yamaha management in the US reacted very positively when they saw my proposal. They already knew of my name from the Inter and Trans-AM races and pushed Kuratomo to finalize the deal as quick as possible.

An early shot of Torsten's 1971 YZ prototype at an international race in Austria. Notice originally the bike shifted on the left. This was later moved to the right as Torsten had ridden Husky's that shifted on right throughout his career.

Torsten at an international race in Austria in one of his first races with his new prototype Yamaha YZ637. Note the Husky seat that Torsten adapted to the bike. We have this very seat in our collection.


   One week later the prototype bikes arrived. They were very trick hand built machines that were completely different than the DT series they were selling. I had received about ten bikes, 125's and 250's. I also selected a few riders to help with the testing to get other input. Tommy Jansson and Janne Lovendahl rode the 125's while Arne Lindfors and Dick Johansson helped me with the 250's. The 1971 YZ125 was an incredible bike. It weighed 139 lbs and was really advanced for the time and Tommy won the 125 Swedish Championship with it in its debut.

   During the initial tests on the 250, the first thing to break was the rear hub. Yamaha designed, built and shipped a new one in about two weeks. This one was stronger but eventually it failed too. A third hub was designed and this one worked without failure. I was very surprised at how enthusiastic Yamaha was and how their resources seemed to be unlimited. Still, I thought that we had a long way to go before the bike would be good enough for international competition. They sent engineers Tanaka and Toshinora Suzuki over to help with the development and any problems that occurred with the bike were addressed immediately. Initially, we had problems with the front and rear suspension and during the many test sessions, the Yamaha engineers in Sweden were communicating with the Kayaba engineers in Japan. New parts were being sent over all the time but the changes that were made were not working so well and the process was taking too long. Kayaba then decided to send two of their engineers to Sweden to work directly with me to speed up the process and after about two months we got the suspension working very good. Even after all the testing, I stilled preferred Koni rear shocks. Yamaha was very serious about building a championship caliber motocross bike and the development progressed much faster than it ever did at Husqvarna.  We got the bike working real good and on July 16th 1971, I entered the Dutch Grand-prix, and gave Yamaha their first grand-prix points with a sixth place.

Near the end of 1971 the bike was developed into a very good bike and Yamaha decided to enter the GP’s for 1972. I recommended they hire Hakan Andersson for the 250 class and Jaak Van Velthoven and Christer Hammargren for the 500 class. Tanaka was now in charge of the motocross GP effort in Europe and contracts were drawn up for each of those riders. Yamaha now had their first grand-prix motocross team. Much of the things learned and modifications made to this bike were directly applied to the 1972 works YZ’s. We moved the engine forward, lengthened the swing-arm, added the reed valve and modified the suspension even further. During the time we were developing this bike, I knew we were making history but never to the degree that it ultimately was. Nearly forty years later the YZ is still going and it all started back in 1971.

Hallman and Tanaka prepare the prototype works Yamaha in the rain for the Dutch GP. Torsten would give Yamaha their first ever GP points that day with a 6th overall.

 Torsten Hallman waits for the start of the 1971 Swedish grand-prix. By this time the bike was developed into a solid GP contender.

Detail Photos


    • The center cases are based on the DT1, while the clutch cover is sand-cast magnesium. The transmission uses hand cut gears that are drilled for lightness and the clutch basket is machined from billet aluminum. As on the Husqvarnas Torsten shifted his bikes from the right side. The kick start lever is forged titanium.


    • This is the first reed valve cylinder. If you look close you can see the weld buildup to house the reed cage. It was made from a piston port works cylinder. The cylinder is chrome bore and the porting layout is much different than anything Yamaha offered at the time. Notice the hand fabricated brake pedal that is actually mounted on the titanium swing-arm pivot. All the motor mount bolts are machined titanium.


    • The air-box is a custom one fabricated by Torsten. The stock one wasn't up to the job. Torsten also took some packing foam that the bikes came in and made a sock that went over the original filter for extra protection. A man by the name of Mr. Bob Tuin (pronounced twin) was there that day and took Torsten's idea and started a company called Twin-Air!


    • Looking at the rear of the bike gives one a sense of just how trick and handmade this bike really is. It is the original prototype YZ. The seat is not recovered, it is an original new one from 1971. The seat pan is hand pound from steel. Check out the special washers at the rear of the seat. There were no silencers in those days. This bike is real loud! Even the fenders are vacum-formed.


    • Up front is a full width sand-cast magnesium hub and magnesium backing plate. The brake pivot is hollowed out titanium. The brake arm is cast aluminum. The brake arm is an updated one that is about twice as long as the initial one. This was for more leverage resulting in more braking power. The fork sliders are hand machined from billet aluminum. Front tire is the original Dunlop sports senior that was on the bike when Torsten raced it last. Even the cable guide is hand made.


    • After the inital rear hubs failed, this was the final updated hub. It is sand cast magnesium and conical in design. The rear sprocket is machined from aluminum and held in place with hand machined steel bolts. This is the original Trelleborg rear tire that was used at the 1971 250 Swedish GP. Exhaust stinger exits at the top shock mount. Oh to hear that sound and smell the Castrol R.


    • The rear shocks are the original machined Aluminum hard anodized Kayabas. The red label is the original label that Identified the valving codes. They weigh just over 3 pounds for the pair! The rear backing plate is sand-cast magnesium and the brake pivot is hollowed out titanium. Brake lever is cast aluminum and the brake arm is machined aluminum. There is a special rear brake cable that goes all the way from the brake lever to the brake pedal on the other side of the bike. This was made extra thick so there wouldn't be any binding. Also with the motor being mounted too far to the rear, this not only hampered the weight distribution, but also made for a very short swing arm. This resulted in too much rear wheel hop. Torsten's extensive R&D work corrected this for the 1972 works bikes.


    • Torsten used Husqvarna handlebars in 1971. The front forks are completely hand made. The damping qualities were not up to standard initially. After Kayaba flew in two engineers to Sweden, and many laps and hours of testing, the fork performance was spot on. The front number plate is signed by "Mister Motocross" Himself.


    • The top triple clamp is sand-cast magnesium and the bottom is machined from billet aluminum. Different off-sets were tested. Hand machined pinch bolts hold the forks in place while titanium is used at the steering stem. The steering stem itself is also titanium.


    • While most works gas tanks are hand pound aluminum, a mold is often used for the shape. This tank was hand pound with no mold. It is a work of art. I have five extra tanks for this bike and each one is distinctly different than the other. It still has the original paint from 1971. These bike have soul!


    • The original Yamaha grips are still there. The throttle housing is a works sand cast aluminum unit. The blue electrical tape and masking tape connected to the throttle housing have survived since 1971! (also note the photos below). Lever covers are also the original ones. Upon close inspection you can even see that the front brake lever still has the slight bend in it that it had in 1971. It is very rare to find a historical works bike that is preserved in the original condition of the day.

 Torsten Hallman's 1971 Yamaha YZ637 is a beautiful bike to look at and represents Yamaha's first real serious effort in developing a GP motocross bike.

 The aluminum gas tank is exactly as it was after the Swedish grand-prix. Each tank was slightly different in shape as they were pound from hand using no mold.

 Say hello to the first reed valve 250 Yamaha. The cylinders were originally piston port but you can see the weld buildup to adapt Yamaha's first reed valve. Note the left side brake pedal.

 The original taping on the throttle assembly remains from 1971 as does the grips.

The rear end sure has the prototype look to it. Aluminum shocks, titanium hardware, mag wheel and external seat mounting really set it apart from the production DT1-MX.

 Nothing standard in this picture, works all the way.

 Torsten's bike autographed by four time world champion Mr. Motocross himself.

Torsten Hallman's 1971 YZ637 prototype Yamaha preserved in all it's glory. 

 Torsten reunited with his 1971 YZ637 in Lake Forest Illinois 2005.