AFT Retro File: The 1975 Indy Mile
Webmaster’s Note: Many moons ago, Kenny Roberts was asked to write a series of articles about his life and career with racer, architect and journalist Patrick Bodden. The 14 pieces that resulted became known as the “Roberts Chronicles,” and were astounding in both subject matter and insight, especially considering the fact they were in the 3-time world champion’s own words. This particular episode, which recalled what’s arguably the most legendary dirt track race in the history of our sport (in which KR charged manically from the back of the pack and won at the last possible moment aboard the tire-spinning, flame-throwing and positively evil Yamaha TZ750 miler), is easily the most famous of the bunch. All of which makes it worth another read as we look forward to the 2018 AFT season. Enjoy!
Even today, people walk up to me and say, “I was at that race,” or, “I was at that mile.”
They don’t have to explain what they mean. I know exactly what they’re talking about – the 1975 Indianapolis Mile, the night I first raced the Yamaha TZ750-powered dirt tracker.
To be honest, I wasn’t exactly enthused about building the thing, this overpowered dirt track miler powered by the four-cylinder two-stroke engine from Yamaha’s brutally fast, 180-mph TZ750 road racer. I really wanted to retain the AMA number-one plate, and with only a handful of mile races on the AMA schedule, I felt we should build a proper dirt track racer, which meant building it around an engine designed for the job.
But Yamaha wasn’t about to do that – too much investment involved. They didn’t exactly disapprove of the TZ-miler project, but they didn’t provide any real support, either. I guess you could say we were on our own, looking for a way we might be able to beat the Harleys, which did have proper dirt track engines, and which were constantly improving.
The idea to build the TZ750 dirttracker came from Doug Schwerma, owner of Champion Frames, a company that built excellent dirt track racing frames, including some of those we’d used on our Yamaha 650 dirt trackers.
At the time, I more or less said, "Go ahead and build it; I'll ride it." So Doug built the first TZ750 miler for Rick Hocking, who rode it at Ascot Park. It wasn’t an overwhelming success. But Hocking demonstrated enough potential in the bike that several more were built. Terry Sage built one for Bud Aksland's brother, Skip; Randy Cleek had one built; and Yamaha Canada built one for Steve Baker. Kel Carruthers built mine.
With an honest 100 horsepower at the rear wheel there was no question the thing would be fast – on the straights, anyway. But all that four-cylinder, two-stroke roadracing-type power came in with a big rush, and it was going to be difficult for the rear tire to hook up. The bike was also relatively light, which only made the traction problem worse. Naturally, there was quite a bit of experimenting with tires to find a combination that would work.
At the time, the only good dirt track tires available to us were 4.00 x 19-inch Goodyear DTs. But they weren’t enough for this bike. Eventually we came up with a workable tire – 18-inch Goodyear roadracing slicks with hand-cut treads. In fact, the Goodyears worked so well they became the basis for the dirt track tires used in racing today.
As for modifications to the big two-stroke to try to get that rear tire to hook up in the turns – well, there weren’t any, really. I did have Kel fit a kill switch directly on the grip that would cut the ignition to the #3 cylinder. I’d press it going into the turns and then let off when I felt the time was right. Trouble was, there’d then be an instantaneous 30 extra horsepower delivered to the rear wheel. The thing just wanted to spin the rear tire and go sideways. When it did hook up, it was fast – 145, 150 mph down the straights, a good 25 mph faster than the Harleys.
The first time I ever sat on the TZ750 miler was before practice for the ’75 Indy Mile. Practice was… let’s just say it was exciting. It became immediately clear that someone was gonna die riding such a bike, or cause someone else to die. I wasn’t interested in either option, so I spent the practice session trying to come to grips with the situation. I was at the top of my game in those days, but I really began to wonder what I’d gotten myself into.
The heat and semi races were no less exciting than practice. When I managed to pass other riders going into a turn, they’d often get past me coming out, and I had to ride like a madman down the straight to pass them back and put enough distance on them so that they couldn't pass me again in the next turn. Basically, the TZ and I clawed our way to a fourth in the heat race and a second in the semi, and we just barely transferred to the main. Had I not figured out during the semi that I needed to shift into fifth – instead of using the TZ's big spread of power to ride the entire track in fourth – I would never have made the main.
The big fun was about to begin. I’d be starting from the last row, and I still hadn’t figured out how to get the thing around the track quickly.
When the flag dropped for the main, the thing sat there spinning the rear tire. I was dead last off the line. When I finally got the bike launched, I passed about ten riders when I hit the straight for the first time. The next five laps were nothing but a blur. Even at the time I wouldn't have been able to say exactly what I was doing. I was just riding on pure instinct.
As the field spread out and things got a bit less crazy, I experimented with different techniques. For the next 15 laps I worked at finding a way to get the TZ to hook up. How fast in, how fast out; precisely where to position myself just before the apex; use the kill switch; don't use the kill switch; throttle position in each case. There were a lot of variables to getting it just right, and it required a lot more precision than you’d think. Of course, the tires were chunking the whole time, so there had to be a conservative/aggressive approach, knowing which path to take under which circumstance.
No matter what, there was no way I could run in the same groove with the Harleys. So I went with this: "Different bike, different track." So, lap after lap, I created my own track, building my own groove, pushing the dirt – the berm – farther and farther out, making it bigger and wider and more solid so I could get a decent drive off it. By then, I was way out there, far from the rest of the racing. When I say far I mean far – all the way to the very edge of the track, right up against the fence and hay bales. I was clipping the bales so hard that the bike came in from the race with straw wedged in it and baling wire embedded in the exhaust pipes! Looking back, it was not the smartest thing I ever did. If I had ever seen my sons Kenny Jr. or Kurtis doing such a thing, I’d have tried to get the race stopped – or I’d have just left so I wouldn’t have to watch something so crazy and dangerous.
Anyway, running my own race on my own track was paying off, and I finally settled into a pattern. But I had to hit every point on the track within twelve inches to keep the bike in the groove, turning the fastest possible lap times. Lap after lap I was passing rider after rider and moving forward.
Eventually, I came up on Gary Scott and Mert Lawwill, who were battling for third entering a turn. Keep in mind I was closing on them entering each turn with an extra 25-30 mph due to the TZ’s massive power. Lawwill decides he can take Scott on the outside, and swings out to pass him. Holy shit! I can’t pass Scott on the inside because he’s right on the guardrail. I can’t pass Lawwill on the outside because – well, because I just can’t turn the thing. But Lawwill swings just wide enough that I make the pass between him and Scott, completely sideways with no room to spare. I really had no choice in the matter; it was a split-second guess that turned out to be correct.
But how many times was I gonna get away with such guesses? And how many times were other riders gonna get away with them as more TZs showed up? Just picture it: six, seven or eight of these brutal things mixing it up with the Harleys, but going 20-30 mph faster on the straights and entering the corners. A rider would have to guess correctly each and every time to avoid disaster. Pitching it into a turn at 150 mph – you’re not going to stop; these things don’t have any brakes, really. You’re not going to turn, as it’s already sliding sideways to scrub off speed. If someone moves into your path, that’s it. You’re just gonna hit him at full speed. I was lucky I was able to fit between Lawwill and Scott when I blew by them.
So for a while it was just me with my own line at the edge of the track. Had I misjudged, jumped the berm and hit the bales, I’d have cleared the concrete wall on the other side and been pitched into the fence designed to catch sprint cars. No way was a rider or bike gonna pass through that with all their parts intact. It’d be like going through a cheese grater. Going through the narrow gap between the pairs of I-beam posts that held up the fencing – well, I think you can imagine. The whole thing was a surefire recipe for disaster.
So far I’d avoided disaster – by inches in some cases.
Five laps from the end I could finally see the leaders, Jay Springsteen and Corky Keener, with Keener having the edge on top speed. I started to think I hadn’t been riding my ass off and risking life and limb for nothing, and that it looked like I was going to get third. I wasn’t sure I do any better that that. But it wasn’t over yet.
Springsteen and Keener were so involved in racing each other that they hadn’t noticed I was catching them. About three laps from the end, Springsteen looked back as I was closing in. I’m sure he must have looked back several times during the race and seen no one. This time was different. There I was, and coming up fast. Springsteen decided he’d better signal Keener, so he pointed rearward with his thumb, then held up his finger to indicate number one, which was me.
But Keener got it wrong. He assumed Springer was indicating to him that no one was behind them and that he – Springer – was going to win the race. The two of them continued racing as they had been, Keener thinking he could relax a bit. Bad idea.
Going into the final turn I closed right up on them. I don’t know what happened, exactly. I shifted up into fifth and that thing got a drive like it’d never gotten during the race. It was like God himself decided the TZ was going to get some serious traction coming off that turn. I was doing my part, straining every muscle as hard as I could to get the bike to hook up. When I nailed the throttle, the bike didn’t go sideways – it accelerated so hard and straight that, for an instant, I thought I might hit Springsteen. But I didn’t. I just blasted past him, thinking, “Great! I’m gonna get second.” But I didn’t stop there.
The next thing Keener saw was my yellow-and-black fuel tank, and he saw it too late. I mowed him down with that TZ miler and beat him to the finish line by inches.
The place went nuts, totally insane. I’ve never seen anything like it. Ever. It was complete chaos. The whole crowd was on its feet, everybody yelling and screaming and jumping up and down. Even people who weren’t there remember that race – along with the comment I made afterward. “They don’t pay me enough money to ride that thing!” People remember that.
It was spectacular, for sure. But it was just too crazy... really, really dangerous. Even the AMA understood that. They knew that with more development, the TZ750 dirt trackers would become missiles, and quickly. And they understood that, even if the TZs managed not to kill anybody in the process, they’d surely kill Harley-Davidson on the dirt tracks. The next year they were banned. You could say it was over before it ever got started.
Fine by me. Riding that TZ750 miler was a helluva experience, and I will always remember the race at Indy in 1975 as my most significant accomplishment on a dirt tracker.
I'm just glad I lived to tell the story!