1968 Yamaha DT-1
Engine: 246cc air-cooled 2-stroke single cylinder, 70mm x 64mm bore and stroke, 6.7:1 compression ratio, 21.3hp @ 7,000rpm (claimed)
Top speed: 71mph (period test)
Carburetion: Single 26mm Mikuni
Transmission: 5-speed, chain final drive
Electrics: 6v, magneto and coil igntion
Frame/wheelbase: Dual downtube cradle frame/53.8in (1,366.5mm)
Suspension: Hydraulic fork front, dual shocks w/adjustable preload rear
Brakes: 5.9in (150mm) SLS drum front and rear
Tires: 3.25 x 19in front, 4 x 18in rear
Weight (w/half-tank fuel): 235lb (100.6 kg)
Seat height: 29.8in (757mm)
Fuel capacity/MPG: 2.5gal (9.5ltr)/35-55mpg
Price now/then: $580/$2,500-$5,000
For most of his motorcycling life, Al Brotz has spent the majority of his time looking through a slight haze of 2-stroke exhaust.
His first bike, at the age of 14, was a used 80cc 1966 Yamaha YG-1. Al and his brother chipped in to buy the little 2-stroke, which ran, but needed some work. Al was excited, his brother, less so. “He rode it once, and then sold his half to me,” Al laughs, adding, “Me? I was hooked.”
King of the field
There was a 40-acre field behind the Brotz family home in Sheboygan, Wisconsin. In the future, it would be developed and a Catholic high school would occupy the site, but at the time, the dirt became a different kind of learning ground as local teens congregated with their minibikes and Honda 50s for a bit of offroad fun. With his YG-1 Yamaha, Al says, he was, at least for a short period of time, the king of the field.
His next machine was a Yamaha YA-1, a 125cc 2-stroke single-cylinder street bike. Out riding one day, he stumbled across an offroad riding area referred to as “The Valley.” Remembering the fun he’d had in the dirt, he attempted to ride the YA-1 up a steep hill, and promptly learned he didn’t have the right machine for the chore. “I was amazed by the guys riding their 250cc 2-stroke Yamahas, and that reinforced my love and excitement for offroad, or enduro, riding,” Al explains. That was also Al’s introduction to the DT series.
Beginnings of the DT-1
Launched in 1968, the DT-1 was a dual-purpose street and dirt machine built expressly for the North American market, and it revolutionized the offroad category. When it debuted, the majority of offroad bikes were larger, generally heavier and more expensive British and European machines constructed for dedicated enthusiasts. Before the DT-1, there was no such thing as a cheap, reliable, simple to ride, truly capable dirt bike.
“Yamaha’s new DT-1 is as American as Coca Cola,” said Cycle World in its February 1968 issue. “The fact that it can be ridden on the street is an added bonus. Very efficient lighting and silencing make the DT-1 a most pleasurable mount for going to the market. Or, if called upon, to make a highway jaunt. The 5-speed transmission allows 60 mph at a modest 6,000rpm, while bottom end is low enough for plonking through the woods.”
There was no earth-shattering technology used in the DT-1; it was just a well-packaged machine based on a tried-and-true dual downtube and single backbone chromoly steel frame. That was, however, something of a departure from the norm in the Japanese industry, where pressed-steel frames were still regularly employed. The rear swingarm was made of rectangular-section steel, with the pivot point for the swingarm placed at the back of the engine case, between the widely splayed rear main cradle tubes. A pair of shocks provided 4 inches of travel for the 18-inch spoke wheel, which carried a 5.9-inch single-leading-shoe drum brake laced into a chrome steel rim. Up front, a 19-inch chrome steel rim was likewise spoked to a 5.9-inch single-leading-shoe drum, with a telescopic front fork offering 6 inches of travel.
“Damping is excellent,” said Cycle World in its review, “and at no time during almost 200 miles in the rough was there any indication of bottoming or topping. The rear suspension is similar in that it seemed to always be soft, but well-damped, never bottoming.” They continued: “Lack of frame flexure and good suspension make the DT-1 one of the finest tracking machines in mud and soft sand, especially at rather high speeds.”
Providing those higher speeds was a 21.3-horsepower single-cylinder, 70mm by 64mm bore and stroke 246cc 2-stroke engine. With a 5-port cylinder, the 2-stroke engine breathed very well. Featuring what would be considered mild port timing, it produced a wide power band, pulling smoothly from idle to full revs, with a predictable and progressive throttle response. An available GYT (Genuine Yamaha Tuning) kit consisting of a single-ring piston, chrome-on-aluminum ported cylinder, expansion-chamber exhaust, central-plug cylinder head and 30mm carburetor gave 1,500rpm to the top end and a claimed 8 horsepower boost, just what the doctor ordered for serious competition duty.
Fuel and air were mixed in a 26mm Mikuni carburetor and spent gases were expelled through a high-level exhaust pipe equipped with a muffler and a wire heat guard. Pre-mixing 2-stroke oil and gasoline was not required, as Yamaha’s Autolube oil injection system took care of those duties. Interestingly, Yamaha delivered the DT-1 with foot controls that could be swapped from left to right to suit rider preference. This was possible thanks to straight-through shafts, including the gear shift spindle.
A simple magneto provided the spark, while a 6-volt generator provided power for the battery and lights, which could be operated even if the engine wasn’t running — a new law in California. Conveniently, the headlamp and taillamp could be removed easily for serious trail work thanks to quick-connect wiring connectors.
A smooth-shifting 5-speed transmission passed power to the rear wheel. Cycle World’s review noted that after a few minutes of riding, most of its testers were shifting gears without using the clutch. “So close are the ratios, and so positive is the shift, that it soon became a tedious chore to bother with the hand lever,” they wrote. Dual instruments were mounted in a removable bracket in front of the wide, braced handlebar, with the speedometer on the left and a smaller diameter tachometer to the right. The rider’s cockpit was otherwise very simple.
Fit and finish was tidy, with an aluminum fender over the front wheel and a slim, 2.38-gallon pearl white gas tank atop the frame, and a seat that Cycle World claimed “induces sleep immediately,” a curious way to compliment its softness and comfort.
Into the dirt
Back to Al and his love for 2-stroke enduros. After seeing the fun everyone else was having on dirt bikes in The Valley, Al sold his YA-1 street bike and bought a 1970 Yamaha AT-1, a single-cylinder, 125cc dual-purpose motorcycle. It was many years ago, in the middle of a Wisconsin winter aboard this very bike, that Al picked up his date, Sherry. They later married, and they’re together still. “She knew what she was getting into,” Al laughs.
Al kept the AT-1 for a couple of years before buying another street bike, a 1972 250cc Yamaha DS-7 twin, a one-year-only model and the forerunner to the RD series. He rode the twin-cylinder 2-stroke to tech school and kept it for a bit before selling it in 1975, and then went quite a few years without a bike.
That changed in 1994. Reading the newspaper classified ads, Al noticed a listing for a 1973 175cc single-cylinder Yamaha CT-3 enduro, with 2,750 miles on the odometer. The bike was 5 miles from his house, so with cash in hand he went to look, and brought the Yamaha back home with him.
“It was 100-percent stock, just the way it came from Japan,” Al says. “And, it was the 175 I was dreaming about when I had my 125cc AT-1. At that point, something tripped in my mind. Having that 175 brought back the sound, the smell and the magic of riding a 2-stroke.”
Al Brotz and his museum piece, a 1968 Yamaha DT-1, with less than two miles on it.
After buying the CT-3, Al made it his mission to form a collection of every enduro model Yamaha made in the 1973 model year, from the smallest 80cc to the largest 360cc. He managed to do just that. Some of the machines he bought were projects and required restoration. Others, like the CT-3, he simply cleaned up and left alone. “I showed them off at bike shows and rode them, especially the 360, quite a bit. But I thought that was the end, I thought I was done,” he says.
Then, in 2016, at the Barber Vintage Festival, Al was brought up short. At the swap meet, he stumbled across the 1968 DT-1 in these photographs. He wasn’t looking to buy another bike, as his collection was complete, but the memories of the bikes in The Valley came flooding back. Plus, the DT-1 had only 1.2 miles — yes, 1.2 miles — on the clock.
“I fell in love with the bike, and kept walking by it,” Al says. “I expressed to the seller that I didn’t have the cash or the means to get the bike home. We talked for a long time, and I told him if he still had the bike in early 2017, I’d like to buy it. When I called him in January of 2017, he said simply, ‘So, when are you coming to pick up your bike?’ He’d held on to it for me.”
This particular example had been a part of the Jim Moon Yamaha collection. Jim Moon, who died early in 2016, and his wife, Peggy, opened their motorcycle shop in 1971 in Springfield, Missouri. Apparently, Jim had set aside some Yamahas he thought might one day be significant examples of the breed. Enter Bob Church. Bob purchased a number of the collectible Yamahas from Peggy, including this DT-1. It didn’t fit into his own collection, and that’s when he offered it for sale — and Al bought it.
“I took over ownership, and all I’ve ever done is dust it. It’s never been worked on, never been out in weather. This thing is spotless, although it is showing a little tarnishing of the alloy, but I don’t want to touch it, it’s only original once,” Al says.
Fittingly, that originality was recognized by the Historic Vehicle Association in October 2017, at the 13th annual Barber Vintage Festival. There, Al and the Yamaha were presented with a National Motorcycle Heritage Award — a large crystal trophy that holds special significance for Al.
The only component of the DT-1 Al has altered is the fuel line, as the original had shrunk off the petcock fitting. He’s kept the original, however. His long-term plans include running the engine with fuel from a remote gas can — just so he can hear it run — but he won’t be putting the Yamaha through its paces.
Al’s DT-1 received the prestigious National Motorcycle Heritage Award from the Historic Vehicle Association in 2017.
“It’s got 1.4 miles on it now, and that’s just from pushing it from the van to the display area at shows,” Al explains. “It’s what I’d consider a museum piece, and I’m not going to ride it.”
He will instead run his 2-stroke 1973 RT360, a bike he picked up from the original owner. Al does fire up his collection of enduro machines on a regular basis, but he continues to ride the 360 on the street and in the dirt, and enjoys nothing more than lofting the front wheel in the air. “You gotta do it,” he concludes, “because these 2-strokes just fly!” MC