1975 Yamaha TZ750

Kenny Roberts' dirt-tracker

1975 Yamaha TZ750

This may be one of the most awe-inspiring motorcycles ever built. In fact, even now, 26 years later, it is legendary as the bike that caused King Kenny Roberts to say: "They don’t pay me enough to ride that thing." Here’s the story: Roberts had won the 1973 and ’74 AMA Grand National Championships using twin-cylinder, four-stroke Yamahas on the dirt. But by ’75, Harley-Davidson’s XR750 had left the Yamaha behind in performance.

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So Yamaha tuners pulled the TZ750 two-stroke, four-cylinder motor out of the road-racer that Roberts used to win Laguna Seca that year, and stuffed it into a dirt-track frame. The engine pumped out 125 horsepower, 50 more than a Yamaha twin. But the question was whether anyone would be able to control the beast.

Roberts tried it for the first time at the Indianapolis Mile, where he quickly discovered that brute power led to a bit of wheel spin. "Finding grip was a problem,’’ is the understated way Roberts explains it today.

The TZ could hit about 150 mph at the end of each straight. But balancing throttle and traction in the corners wasn’t easy.

Somehow, Roberts qualified for the 25-lap final. And off the line, he put himself in sixth place. But he admits that keeping the bike on the track took every bit of skill he possessed.

"In the main," Roberts recalls, "the cushion went right up to the hay bales. After the race, I had baling wire on the bike" from bouncing off the bales.

In spite of all that, Roberts closed on the leaders: Harley riders Rex Beauchamp, Corky Keener and Jay Springsteen. Then, on the last lap, "I got a terrific drive off turn three. I have no idea why. The tire was almost gone, three-quarters chunked.

"Coming off the last corner, I definitely had third, and I thought I could get second. I hit fifth gear and it was less than a quarter mile at 145, so everything happened quickly."

Somehow, Roberts got the TZ hooked up, and in the final feet of the race, blew past the Harley trio for the win.

It was a spectacular debut, but it was also the bike’s only moment of glory. Roberts tried to ride it at two more races, but reverted to his twin both times. At the end of the season, the AMA wrote new safety rules outlawing such machines in the future.

Eventually, this incredible motorcycle came into the hands of historian Steve Wright. It was previously on display at the Motorcycle Hall of Fame Museum at AMA headquarters in Pickerington, Ohio.

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Year Built
1975

Engine
liquid-cooled, two-stroke, four-cylinder

Displacement
750cc

Bore x Stroke
64mm x 54mm

Carburetors
four Mikunis

Transmission
six-speed

Owner

Steve Wright

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