By the mid-1970s, Yamaha was responding to market forces that indicated the days of two-strokes were limited. Yamaha decided to build a new four-stroke flagship for the dirt, one that would take over for the Honda XL350. The plan was to build a full-sized, four-stroke, single-cylinder, dirt bike that was similar to the famous British BSA singles in performance but with better reliability. It was code named the YR400. Since Japan had a “tiered” driver’s license program that limited younger riders to 400cc, Yamaha chose 400cc as the displacement for the Japanese domestic models and 500cc for the American market. By late 1975, the street-legal XT500 was released. A few months later, Yamaha introduced the dirt-focused 1976 TT500. It was 15 pounds lighter and devoid of the XT500’s road equipment. The TT looked like a motocrosser with its number plates and simplified but bulky exhaust system.


Tom White said, “For my new company, White Brothers, the TT500 was like a shot of nitrous. I had hoped for a more serious four-stroke race bike, but the TT500 was very versatile. Even when fully modified, the TT500 was never as good as my super-trick 1974 BSA B50; however, the Yamaha TT500 was the right product at the right time. It sold well, and White Brothers, Powroll and Pro-Tec sold a boatload of hop-up parts for it. White Brothers offered everything from 36mm Mikunis and high-compression pistons to big-bore kits to Terry fork kits and Hallman-Lundin frame kits.”


The TT500 was a home run for Yamaha. In addition to the TT and XT500, Yamaha introduced the SR500, a strictly street bike that was produced from 1978 to 1982. Yamaha reintroduced the SR500 as a 400 in Japan in 1994 and sold thousands. Yamaha’s biggest four-stroke success—the YZ400—wouldn’t come along until 1998. It changed motocross as we know it.


“Suggested retail in 1976 was $1395. MXA’s featured bike was purchased at Rustan Motorcycle Sales in Midway City, California, then delivered to White Brothers where it had a WB001 Hi-Pipe and Pro-Tec Hi-Volume oil lines installed. It was ridden for 50 miles in the desert and then parked for 40 years,” said Tom White. “The TT500 put White Brothers on the map. It’s priceless to me. The TT500 was the only motocross four-stroke that Yamaha offered in 1976—although it was part of a larger family of single-cylinder 500s that included the XT500 and SR500. For the collector, the rules are ‘stock is best’ and ‘first-year models.’ Good luck finding a stock TT500, as almost everybody modified their TTs. The original tank, pipe, and carb would be desirable to any collector other than a White Brother.”

For more info go to the Early Years of Motocross Museum site at


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