RockMoto

Just look at the mutant motorcycle in the photo above.

A 750cc two-stroke road racing engine. Dirt track frame and tires. No front brake, of course. A garish, yellow Frankenbike with 120 horsepower. Built to win on the one-mile long, horse-racing style flat tracks that were part of the Grand National Championship circuit, the premier two-wheel series in mid-1970s America. This abomination was an act of engineering desperation.

In grade school I remember watching black and white footage of the early days of aviation. One enterprising engineer decided it would be a good idea to strap crude rockets to his back while wearing ice skates and would-be wings. The thinking was: lean forward, light the fuse and go flying. Predictably, by the end of the short film clip, the intrepid rocketman’s assistants were jumping around doing their best to put out his raging ass fire.

The TZ750 miler of 1975 was the motorcycling equivalent of that insanely bad idea and it was ridden three times in battle by one of the greatest riders in history, Kenny Roberts. Except that during one historic night, Roberts made it work. In fact, he made it win.

Last year at the MotoGP in Indianapolis, I met Roberts after an expensive meal in perhaps the most high-end restaurant in the city. A mutual friend came by the table to exchange a few words, and there next to him was the two-time Grand National Champion and three-time 500cc Road Racing World Champion. The King himself. Only five-foot-seven, a rather small man but with very, very big balls. Pardon me, but facts are facts.

I didn’t stare, but it appeared that KR was wearing Crocs, those funky, vented, rubber, strap-on clogs favored by gardeners. I wondered if the airline had lost his luggage. Or maybe a local Mayor McCheese had invited him to some groundbreaking ceremony and he didn’t want to dirty up his nice loafers. More likely, it’s accepted that once you’ve been the baddest motorcycle racer on all the planet, you then get to wear whatever you like on your feet and that’s all there is to it. Fine by me.

In 1975, the TZ miler showed up to its first race, there in Indianapolis, and it shockingly stuck out among the other bikes at the track - much in the way that Kenny’s outdoorsy footwear likely caught the eye of the restaurant’s maitre d’. The engine, four-cylinders across, was designed to win the Daytona 200, the Imola 200 and all manner of other open-class road races. This was a purely pavement powerplant.

Major dirt track events were being won by twins. Still are. Booming four-stroke twins. Narrow. Relatively light. With broad powerbands, to help the chunky, but not knobby, rear tires hook up to the smoothly manicured soil. With a gaping wide radiator and four expansion-chamber exhaust pipes, the liquid-cooled TZ was a two-stroke and it didn’t boom at all. It ring-dinged like a killer buzz saw. It was a screaming punk rocker wandering into a hillbilly hoedown and picking a fight.

A unique sound is one thing. But compared with the four-strokes, the TZ was severely handicapped by a super-peaky powerband that violently spun up the back tire. Limited traction means limited control and limited forward thrust, and forward thrust has always won motorcycle races. The TZ engine was designed to work with a slick tire tenaciously gripping on pavement. Kenny had some 40 horsepower on everyone else that night. But on the dirt it came with a hefty knife-edge price.

Traction control? In 1975, it amounted to a handlebar-located switch that could kill ignition on one of the four cylinders, and help try to tame the bike’s vicious power. But Kenny was in a tough spot that season. His own four-strokes weren’t powerful enough anymore, and the No. 1 plate he was wearing for the second straight year was slipping away. He had to take a chance on the TZ.

Roberts started the Indy Mile in back. His lines around the big fairgrounds oval were as unorthodox as the bike. Instead of sticking down low, where the other bikes circulated, Roberts rode up high, which was the long but fast way round for the TZ. Heavy hay bales lined the edges of the track and twice, he hit them. But he was making up ground.

The main event was 25 laps and it’s possible that no motorcycle racer has ever ridden longer on the limit than Roberts did that night. Corky Keener and Jay Springsteen had been riding up front, both thinking that the race would easily be won by one or the other. Somehow, Roberts forced the TZ to hook up coming off the last corner of the last lap, putting the power down and sling-shotting into the lead for the only time during the race, right when it mattered.

It was the only time that a two-stroke had ever won a Grand National mile. Thanks to the magic of YouTube, you can watch highlights here: http://bit.ly/4wW0z.

“They don’t pay me enough to ride that thing,” Roberts was widely reported to have said. He ran the TZ in two more, unfortunately futile, races. He lost his crown that year and the bike was banned by the sanctioning body, without any argument.

Kenny Roberts went on to worldwide fame as a three-time 500cc Grand Prix champion and he retired from full-time competition after 1983. But his greatest ride, perhaps the greatest ride ever, just might have been behind the bars of this monstrous TZ750 miler.

In any case, he's got big Crocs to fill.