The time line for off-road motorcycles should begin in 1968 with the birth of the Yamaha DT-1. Previous to that date should be classified as “BDTE” (Before DT Era) and after that should be “ADTE” (After DT Era). That’s how significant the first dual purpose bike is, and was.
BDTE there existed only English four stroke singles and twins that were heavy street bikes stripped of their street gear, underpowered, quirky and lovingly referred to as Desert sleds, and the European two stroke singles that were light and powerful and as easy to get and maintain as a Panda Bear. The DT-1 was the motorcycle equivalent of the Ford Mustang in that it brought thesense and sound of a European motor exotic to the doorstep of the neighbor down the street in small town Iowa. All at a price and maintainability that anybody could afford, and do. If you had the luck of a lottery winner, it would be on your doorstep in the morning.
The DT-1 was the first dual purpose bike in that it was exceptional in both worlds, without any changes made to it. All you had to do was visit your local friendly Yamaha shop and lay down $580 ($3,360 in 2006) to the salesman, start it up and ride into a new adventure. The only comparable bike at the time was the hard to pronounce Swedish bike the Husqvarna ( Whoossk-Var-Na) 250 enduro. It was great bike off-road as it was based on the world championship 250 MX bike, but not to good on the street. Essentially a MX bike with lights thrown on that cost $950 ($5,500 in 2006). The DT-1 in comparison weighed about the same, had equal horsepower and was 40% less expensive. Did I mention that there was a Yamaha shop on almost every corner in the country? Not that you had to work on the bike at all, but parts were cheap and if you actually needed them they were available within a week or two from the United States distributor in Los Angeles.
One year after the Summer of Love in 1967 the effects of peace, tie dyed clothes and psychedelic posters still hung in the air along with other pungent smells. You could feel a revolution was coming your way. We were no longer tied down to decades old British technology and tweed coats, or Swedish minimalist engineering. We had a bike that was designed for the swinging American youth and the big country they lived in. It may have been manufactured in Japan, but it was our American bike. The DT-1 was a bike you could ride to High School, and when school let out you could go for a ride on the fire roads to release that pent up teen age angst. Crack the throttle and open up your mind to a new world. It was also a bike you could easily ride to the track, take off the lights and throw some pie plates on and go racing for the day, and then ride it back home as sunset fell. It was Yamaha’s philosophy that you watched the flow of the market and changed rapidly with it to develop new original products for what the customers wanted, and not the engineers or accountants. After two years of quick development and production, The DT-1 mirrored that thought and became Yamaha’s step into the future. In the first year 12,000 units were produced and sold out. Previous total sales for all off-road bikes were 4,000 units. La revolution had begun mes amis.
There was a new sport being introduced to America in 1967 by the American Husqvarna distributor Edison Dye. Edison brought over the best riders in the world to have a little vacation in America during the summer break of the World Championship season, and to put on a new race series called the Inter-AM (International-American) competing against the very green American racers. Who were these barbarian invaders from Europe? Swedish and Belgian champions Torsten Hallman, Joel Robert, Roger DeCoster, Hakan Andersson, Ake Jonsson and many more. For every kid who saw those races it was goodbye to the American dirt track and scrambles races and HELLO to a three moto race of thirty minutes each with Olympic scoring. It was like your children had been abducted and brain washed by aliens. Which in fact they had been. Now the Japanese manufacturers of Yamaha and Suzuki were on the fast track to build bikes to meet this fastly expanding market. Where was Honda? They were busy building road racers and sticking to building only four strokes. They left the building of two strokes and motocross bikes to their smaller Japanese rivals.
America now had the basic bike for a new wave of young enthusiasts to tinker and fidget with to make faster and lighter to race motocross in. Now every back yard garage tuner equipped with a welder, drill, grinder and a little bit of knowledge could let their imagination and delusions run wild. There was one person however who had all the pieces and intelligence necessary to take that evolutionary step.
As the famous car racer Carroll Shelby turned his racing background into modifying the new Mustang cars into the race winning GT 350 Pony cars, so did his motorcycling equivalent Don Jones turn the DT-1 into a National Championship winning bike called the YZ. Don had come from a long dirt track racing background after WW II competing at Daytona and nearly every west coast dirt track. As every racer in that time they learned how to work on and tune their motorcycles, and more importantly how to modify their warmed over WR and KR Harley’s for the racetrack. Ingenuity of how to make something lighter and faster to beat the other guy always ran through each racers head. Yamaha’s first contact with America was in 1957 when Frank Cooper, of the famous importing company Cooper Motorsports, went to Japan and brought back 200 Yamaha motorbikes to the U.S. Quite possibly the first Yamaha dealer was Don Jones and his partner Bob Wright’s Rosemead Cycle Shop. Three more years and Yamaha setup their own distributor in Los Angeles, Yamaha Motor Corporation, USA. Ten years after the Yamaha’s first contact with Jones, history would repeat itself.
It started when Dennis Mahan, who was the manager of the race team and Research & Development for Yamaha, came knocking at Don’s door in 1967. Dennis was previously the mechanic for national #10 dirt track racer Neil Keen who rode BSA Gold Stars out of Don’s shop in the 60's. During the west coast racing season they would work out of the shop and during the off season Dennis would prep the bikes for the next season and work in the shop for extra money. Or as Don tells it, “In 1967 we were racing BSA and Triumph’s. Dennis came to us and wanted us to ride the 125cc AT-1 and I told him that it was a piece of crap, that was heavy and a little old street bike. Dennis told me that Yamaha would provide us with a bike, parts, entry fees and bonuses if we won which was much better than what the English companies were offering at the time. So we went about making the AT-1 into a race bike. We later bored out the cylinder an upped it to 175cc, but we were still competing against European race bikes like the DKW’s and Penton’s who were also secretly pumping their engines up to 175cc. I know that for a fact, because I was boring it out for them at our shop. Dennis told us to hang on because in a few more months we are going to have a 250cc bike for you.
The initial shipment was for three DT-1's and then followed up by two more bikes. One bike was made into a TT dirt tracker that Keith Mashburn raced, Neil Keen raced one in short track and Gary and DeWayne (Jones) shared another one. That bike was dangerous ridden at speed so we knew that we had to make it lighter, faster and handle better. Then came the process of testing, changing them and racing. Then start over again and again.”
The first thing that Don Jones did was to look a the engine. The DT-1 was well designed as to being almost bulletproof, but to be competitive it needed to be pumped up from it’s stock 22 HP to at least 30 HP of the current crop of MX bikes from Europe. The original DT-1 did not come with a reed valve. Don knew from previous experience that this needed to be changed immediately. First on the list. Unlike today’s monster sized reeds the first Jones reed was almost invisible to the eye, but not to the performance of the engine. Jones says, “We put the reed valve on to get some bottom end power out of the motor. With a piston port motor you have to stuff as much gas/air mixture into the cases without leakage for the most amount of horsepower and torque.” This kept the gas/air mixture from blowing back through the carburetor and charged the cylinder for more combustion. The crank was drilled for lighter weight so the engine could pick up the revs faster and then stuffed with aluminum plugs to keep the combustion chamber pressure high. The helical drive gears were replaced with more efficient and noisier straight cut gears for less mechanical friction loss of horsepower to the rear wheel. The gearbox gears were individually drilled to reduce weight. Different sized rods and pin placements were tried many times to find the optimal horsepower range. They replaced the stock steel bearing cages on the rods for the Yamaha road racer bearings that used aluminum and bronze bearing cages that held up under the pressure of revs over 8,000 RPM. A ignition was taken off a Kawasaki 100 with a button electronic ignition to eliminate the points ignition and once again lighten the load on the crank for faster response from the throttle. Using wooden molds to sand cast the cylinder, the head and the reed valve block was all done in housealong with any thing else that needed being made. The clutch cover was made from Magnesium for weight reduction and also to get rid of the oil injection unit from the DT-1. The motto was if it didn’t work you didn’t tell anybody, and if it did work then you told them. The original GYT (Genuine Yamaha Tuning) kit for the DT-1 model included a chrome lined cylinder. The reasons for a chrome cylinder were easy in that the aluminum cylinders were now directly connected to the aluminum pistons so that the expansion of both grew at the same rate. Previously the pistons made out of aluminum expanded at a faster rate than the iron cylinders causing frequent piston seizures causing the engine to lock up and pitch the rider on his head at speed. With the chrome liners you could now run a much tighter tolerance of the piston to cylinder and therefore increase horsepower. Yamaha was the first major manufacturer to use the chrome liners on their production Yamaha road racer in 1966 on the TD-1B racers using a porous liner to retain oil.
The problems were that the early chrome liners flaked and chipped causing engine blowups. Anytime you ported the cylinder you would have to re-chrome the cylinder again. Jones originally chromed the AT-1 cylinders and chromed the YZ cylinders also using his own process. The one thing that you do with any engine it to open it up and let more gas/air mixture in and out of the engine. On a two stroke you do that by porting, carbureting and exhaust. The carbs were moved up to at least 34mm, the exhaust was made out of stove pipe that was thin, strong and light with changes to the pipe dimensions to keep the mixture in the engine and porting get the gasses in and out and all around. After all was said and done the YZ not only made the 30 HP goal but surpassed everything in the field including all factory bikes by pumping out 40 HP! Almost a 100% improvement and a 18 HP improvement in engine performance.
The American YZ, was originally called the “A to Z” because it had borrowed a little bit of this and a little bit of that from other bikes ranging from A to Z. With the engine in hand the rest of the bike was next. Don Jones said, “The Yamaha DT-1 engine was bulletproof and had good horsepower. For some reason they just didn’t handle right. We changed everything in the world on that bike. Moved the engine up and down, back and forth. Had swing arms short and long. Different length forks and different steering angles. When the kids would come in and say this baby handles good. So we would let other people then try it. That was our measuring stick of what worked and what didn’t. On the first stock DT-1 frames we did add two inches to the frame to lower it for better handling, but we were never happy with that and especially re-welding it back up without being able to treat the weld, and we broke a bunch of those frames also. We built our new frames on the wreckage of those frames to get one that worked. Ernie Reed from Missile Welding Company was a sub contractor to JPL (Jet Propulsion Laboratory) and did the welding up of frames for us starting up with our BSA and Triumph frames. Ernie would show us a drawing they made for a frame and we would look at it and talk about it, and then look at it again, and talk about it some more. Then we made a couple of frames that we didn’t like, and then made a few more that we liked better. After all the inputs and experience from the prototypes we came up with a final specification that everybody agreed was good.. So we designed the frame and Ernie jigged it and welded it up for us. We made a lot of chrome moly frames and we did make six titanium frames mostly just to save weight, plus the Japanese also wanted them. Out of the six frames, four of them went back to Japan. I don’t know what happened to those frames because I don’t even have one of them myself. We even had an adjustable fork crown where we could adjust the steering angle. We also tried to make the swing arm horizontal for better power delivery and handling.
The stock shocks from Yamaha would get hot very quickly and the dampening would disappear just as quickly. Yamaha sent us four engineers and along with myself, my son DeWayne, test rider Rudy Galindo, Dennis Mahan along with desert racer Mike Patrick we tested the shocks on a run from Barstow to Vegas. The next morning in Vegas it was 23 F degrees and the shock would hardly move. No one wanted to ride the bikes in that condition. The shocks leaked oil. When we got home we decided to put some lighter weight ATF oil in the shocks and we thought that they needed more oil capacity and so we built some reservoirs and welded them to the shocks. That was how the Yamaha Thermal Flow shocks were created.
The first DT-1 forks came with steel sliders and they were heavier than hell. We originally used CZ and Betor front aluminum fork sliders because you could slide the stock 35 mm fork tubes in them and then turn them down on a lathe and you couldn’t tell if they were from Yamaha or not. Later we cast our own sliders which were pretty good, but we still broke a bunch of those fork legs we made. The sliders needed to be forged for increased strength and Yamaha started making them that way. The whole idea was to make them lighter and stronger than the original stock sliders.”
On the prototype the front brake was a full width Honda unit and Jones said it stopped real well and was light. The conical front hubs that found there way to the YZ came actually from Yamaha and were most likely patterned from the European CZ, Huskybikes. The kick starter and the swing arm and rear wheel axle were made out of titanium. The front axle was chrome-moly with the center drilled out for weight savings. Every nut and bolt on the bike that could be drilled out was drilled out for the smallest amount of weight loss.
The seats on the Yamaha were huge for the day and that was because it made up for the lack of rear travel. “Bates” the famous leathers manufacturer in the 60's and 70's also made seats, seat covers and foam at the time. Since their was only four inches of rear suspension, Don asked Bob Bates to make up a seat like the desert racers used at the time with lots of padding. A big firm seat for your rear end was a good replacement for a lack of suspension travel.
One of the most striking and identifiable pieces on the bike is the aluminum curved tank with the factory straps. How did this get designed? “We designed the YZ gas tank for the first reason because we needed a tank that could run a 40 minute moto plus two laps as required for international races back then. To tell you the truth I took a Bultaco tank and an Ossa tank and chopped those up and fiber glassed them together. I sent it down to my employee Dan Hillibig who made our fiberglass shop products for BSA and Triumph’s such as gas tank/seat combos for the Trackmaster Frame Company.
We were ready to go racing and we just got these new tanks out of the fiberglass molds. We didn’t know exactly how we were going to put mounts on the tank to hold it in place yet. We didn’t want to mount it in the center with a bolt attached to the backbone of the frame. So for the first one we used a rubber bungy cord on the front of the gas tank around the gas cap to hold it down and another on the back of the tank. The next week we went to a horse bridle shop and used the velcro cinch materiel and fitted it to the gas tank to securely mount the tank. We sent the bike over to Japan so they could see everything we were doing on the bike and Yamaha liked it so much that when they first came out with the real factory YZ Yamaha’s they copied the gas tank mounting system using velcro straps.”
All this time Don Jones had a company called “The Jones Factory” that made MX grips, wheel foam inserts for shouldered rims to keep the mud from accumulating and various fiberglass tank/seat combinations including the original YZ styled gas tank. In addition to many parts for bikes such as reed valves and those cool magnesium clutch covers Now everybody could attempt to make their own American hot rod. Just like that car fellow Carroll did.
When the YZ was done the weight savings dropped the bike down to 189 lbs.
The HP to weight ratio for the 1970 YZ Yamaha at 40 HP and 189 lbs = 1 HP for every 4.75 lbs. In comparison the 2007 Yamaha YZF 450 at 220 lbs and 50 HP = 1 HP for every 4.4 lbs.
Matching size to size the 2007 Yamaha YZ 250F at 204 lbs and 30 HP = 1 HP for every 6.8 lbs. So after almost 40 years hardly any improvement even with an engine almost twice the size in the go fast kick in the pants category. What about the original DT-1? The 1968 DT-1 had 22.1 HP and weighed in at 231 lbs for a 1 HP for every 10.5 lbs. You know? A slug!
The bike was also being developed in 1971 by four time 250cc World MX Champion Torsten Hallman on the World Grand Prix circuit and at home in Japan. So how much of Don Jones/Dennis Mahan’s work made it’s way into the bike? Hard to say, but the shocks, tank, seat, forks, clutch cover all were a Jones creation. What about the engine? Don tells a story of his being a little pissed off at Yamaha. “All the bikes for the Europeans came directly from the factory in Japan. There was a race up at the Staddle Line track in Olympia, Washington where they got one of my bikes and it was so much faster than their factory bikes. Hakan Andersson, who became the 1973 250cc World Champion, and four time 250 World Champ Torsten Hallman kept saying that they wanted “My cylinder. My cylinder.” There was no way we were going to give up that cylinder or anything else to them. Andersson threw a rod in his engine and asked us if he could borrow an extra one we had. I agreed only if they gave it back to us after the race. Well, the race ended and they took off with the engine in their hands. I was so mad I couldn’t see straight. Terry Tiernan told me that engine belongs to Yamaha and not you. Needless to say I didn’t like that they stole a couple of engines from me.” The difference was that Yamaha in Japan sent the Europeans the bikes to be modified, and the Americans sent the Japanese their bikes to be copied. In this case the egg came before the chicken. The “A to Z” engine was the toast of it’s class and the production YZ was also the HP king. Need I say more.
So how did the bike do in competition? The inaugural AMA 250 Championship in 1971 was on the “A to Z” bike in the summer Inter-AM series where Gary was the top finishing American. In 1972 the AMA had it’s first stand alone 250 championship series and Gary won the 2nd of his championships on a Yamaha leading 2nd place finisher Jim Weinert also on a Yamaha by 995 points to 781. Gary also finished 2nd in the 500cc class riding the 360cc YZ behind champion Brad Lackey on his Kawasaki. Marty Tripes won the first ever Supercross race at the Los Angeles Coliseum as a 16 year old in 1972 on a Yamaha YZ. Dennis Mahan hired both Gary and Marty. After that Gary left to race and win for Honda on their first year Elsinore in 1973 and then on to Can-Am where he won his fourth straight AMA 250cc MX Championship. Don and Gary in 1975 went on to build the famous, or infamous, AMMEX 250cc MX bike in a joint effort with the Mexican motorcycle company. Dennis moved in 1973 to work for Can-AM where they rejoined efforts once again to make championship. But that is another story to tell.
Don says that, “The only way that the bike ever came to be was a team effort with Dennis Mahan who was at least 50% responsible for the development of the bike every step of the way. After the initial work was completed Sonny Nagashima from Yamaha was our connection to the factory and we spent days and nights all together in the shop that Yamaha gave us to come up with a better way. The support from Yamaha was great. Terry Tiernan who was the V.P. for Yamaha of America, and all of our bosses, told us “The sky is the limit. Do anything you want to make this thing better.” There were so many, many things that we did.” The other part of the team is the Jones family of sons Gary and DeWayne who tested and broke every part over and over again in practice and competition with a big smile on their face of wanting to do it again and again. When they weren’t riding they would be working in the shop making the parts so they could go faster and faster. Even the jerseys were made by their mom sewing the names and numbers on the football jerseys.
Don wraps up his experience with the YZ in typical racer talk,“Yamaha never paid us for all the work we did, but they did pay for the rent of the building and the expenses for this and that. We were never under any contract to build anything. They were really getting it for nothing. We were more interested in winning a race and becoming a national champion than in developing a new bike. But you had to have one before the other.”
The combination of Japanese engineering and American ingenuity to produce a product for an emerging market transformed the DT-1 into the famous YZ 250. The 1968 DT-1 in very good shape can go for over $10,000. Tom White’s DT-1 in the pictures here with 46 miles on the odometer is valued at $25,000. The 1974 YZ 250A in excellent shape goes for $10,000 and the limited edition YZ 360 for $13,000. The price of an “A to Z” bike? Don’t even ask. The name is Don Jones by the way, not Carroll Shelby.