CLASSIC MOTOCROSS IRON: 1971 YAMAHA RT1-MX 360 (GYT KIT INCLUDED)

By Tom White

Inspired by the success of the DT1 and AT1 a year earlier, Yamaha pulled out all the stops to release the beautiful black 360cc RT1 to the public in early 1970. Rumors had been circulating since the DT1’s release that an Open-classer was in the works, and the big Yamaha was almost everything the fans expected.

Our 1971 example is finished in gorgeous black with red pinstripes. The 1970 RT1 was nearly identical but featured yellow pinstriping. As with the other Yamaha dirt bikes of the period, there was a street-equipped Enduro model and a GYT-kitted all-out motocrosser. The RT1-MX had the same frame and running gear as the DT1 Enduro, and the only concessions for motocross were stripping off the lights, the 21-inch front wheel, expansion chamber and a high front fender. The most attractive thing about the RT1-MX was the $995 price—and the included front number plate sealed the deal for first-time Open bike riders.

dt360side

The piston port engine’s engine cases, transmission, clutch and ignition were similar to that of its 250cc sibling. Bore was increased from 70mm to 80mm, and the stroke was increased from 64mm to 70mm. The installed GYT kit (Genuine Yamaha Tuning) featured a center-located spark plug head with higher 7.2:1 compression, a ported cylinder, 34mm Mikuni, and expansion chamber exhaust. Strangely, it kept the Autolube system. The result was an impressive 36 horsepower—six more than the RT1 Enduro model.

Besides the price, the best thing about the RT1-MX was the bike’s reliability. Because Yamaha was entering virgin offroad territory with the DT1 and RT1, its engineers over-designed the parts to ensure that there were no weak links. Never a serious Open-class motocross bike, the RT1-MX was a popular entry-level racer, desert bike and enduro machine.

1971 YAMAHA RT1-MX 360 FACTS

WHAT THEY COST?  There are still many DT1’s and RT1’s in use some 48 years later. Although not popular with collectors, they are an inexpensive way into vintage racing. Expect to pay around $1500 to $2000 for a decent example which is about double the original $995.

MODELS? For motocross the AT1-MX (125), DT1-MX (250) and RT1-MX (360) represented Yamaha’s motocross lineup.

WHAT TO LOOK FOR? The body work was often changed to the detriment of the bike’s value today—as in Preston Petty fender or Vesco gas tanks. The oil injection system was usually removed also. Collector’s want all of the original stuff, especially the stock GYT expansion chamber. Aftermarket Bassani or Hooker pipes are not as valuable as the stock pipe. There is a huge bonus for the original Yokohoma tires.

PARTS SUPPLY? Speed and Sport at (570) 784-6831 is a good source for older Yamaha parts.

For more info on classic bikes go to www.earlyyearsofmx.com

 

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