CLASSIC MOTOCROSS IRON: 1971 YAMAHA DT1 MX
BY TOM WHITE
When Yamaha introduced the Yamaha 250 DT1 in 1968, it was an immediate success. Don’t misunderstand; it was not a great street bike, trail bike or motocross bike, but it had possibilities in all those uses and was priced right at $580. With the dirt bike market exploding in the late 1960s, Yamaha developed a GYT kit (Genuine Yamaha Tuning) for the DT, which included a ported cylinder, piston, cylinder head, carburetor and expansion chamber. The GYT kit retailed for $200 and, when installed, upped the power from 21 horsepower to 30 horsepower (a number that got it in the league of the CZs, Huskys, Bultacos and Maicos of the day).
In 1970, Yamaha released the DT1 MX version. It had the speedo, tach, headlight and taillight stripped off. The 19-inch front wheel was replaced by a 21-inch wheel, and knobby tires were standard equipment. Best of all, the GYT kit came already installed, although Yamaha retained the Autolube system that allowed the DT1 to run straight gas in the tank instead of premix. Also standard on the DT1 MX was a high front fender, but it the kept the enduro rear fender (including holes for the taillight). The most attractive thing about the DT1 MX was its $895 price tag; however, serious motocross racers never considered the DT1 MX when it came to choosing a race bike. Entry-level dirt bikers were attracted to its low price and large dealership network. In 1971, Yamaha had a full line of motocross bikes, including the motocross 125cc AT1 MX, 250cc DT1 MX and 360cc RT1 MX. You have to remember that this was three years before Yamaha would build its first serious motocross bike, the YZ250A.
Given that the AT1, DT1 and RT1 were not true-to-life motocross bikes but warmed-over, dual-purpose machines, it is hard to find an original example that didn’t have Preston Petty fenders on it, the steel gas tank replaced and the oil-injector system removed. Vintage collectors want all the original stuff. A simple item like a DT1 front fender can now cost $250. Hard-to-find parts include the stock GYT kit expansion chamber and original Yokohama tires.
In the hands of a capable tuner, the DT1 could be turned into a potent weapon, and Yamaha hired the Jones Gang—father Don and sons Gary and DeWayne—to develop the DT1 MX. Using the DT1 MX as a starting point, Gary Jones won the 1971 250 National Championship and would retain it in 1972, while 16-year-old Marty Tripes would win the Superbowl of Motocross on one.
The Yamaha DT1 MX was the last dual-purpose-based bike to ever win major professional races—from this point on, it was purpose-built race bikes. For more info go to www.earlyyearsofmotoctossmuseum.com