The 145mph T2750 Flat Tracker BANNED BUT NOT FORGOTTEN
Sideways scrubbing. Looking for traction. Riding what is one of the nastiest machines ever made. There’s a reason why many in the racing world love and fear these things. Not least of all because of how they bite. And how often they can.
The motorcycle world stopped when Kenny Roberts climbed aboard Ray Abrams’ Yamaha TZ750 flat tracker at Indianapolis in 2009. He rode it like he stole it during that famous Saturday evening demonstration during the Indy Motogp weekend – as only the great King Kenny knows how. But that wasn’t his first time at the Indy Mile on a TZ750 flat tracker. His first appearance became famous after Roberts proclaimed, “They don’t pay me enough to ride that thing!” It was a comment that later helped AMA officials decide to ban it from competition. The saga started in early 1974 when Steve Baker and mechanic Bob Work stopped by to visit Doug Schwerma at Champion Racing Frames, in California. The pair were on their way home after picking up the display Yamaha TZ750 road racer after the Anaheim dealer show. One idea lead to another and Schwerma, who was already making Champion frames for AMA flat trackers, measured it up and compared it side by side with an XT650/750 Champion frame to see if it all fitted. It did, however he had to wait quite some time before he got an engine to build a frame around, and when he finally did, in 1975, it was history in the making. Renowned race bike builder Ray Abrams, of A&A Racing in San Francisco, built up the prototype using a Champion chassis, which enjoyed similar frame dimensions to the 650, but he already knew its potential! “There used to be a quarter-mile drag strip across the bay in Freemont, and I took the bike over there when it was still in the road race frame and it turned 138mph in around 9.5sec in its stock form. So we knew it was going to be a whole lot faster!” Abrams says, laughing. “It was really going overboard developing something nasty because it was a whole lot faster! Almost everything was different. The tyres didn’t work as well because we were putting more power through them, but we did what we were capable of doing at the time.” The prototype was built for the Mile ovals but was tested by Rick Hocking at the Ascot Half Mile in Gardena, California, in 1975. The problem was that by 1975, Harley-davidson’s alloy XR750 had become more competitive, which left the XT650/750 underpowered – and behind on the long straights. The TZ750 flat tracker was the obvious instant solution, plus most engines came from readily available donor road race machines supplied whole, by Yamaha. Interest in this big-balls idea increased after Hocking set the third-fastest time during Ascot on the prototype, and it wasn’t supposed to suit half-mile tracks. Abrams again: “My bike was originally built for Hocking. I don’t think he complained about anything. Ascot is a perfect place for a motorcycle, as you can spin the rear wheel and it’s easier to control. I don’t think there were any major problems there, and Rick was a guy, like Kenny, who was capable of riding anything you put underneath him!" Five other TZ750 flat tracker frames were made for 1974 AMA Grand National champion Kenny Roberts, Steve Baker, Randy Cleek, Skip Aksland and Don Vesco. This was at a time when the Grand National consisted of several disciplines, where Yamaha riders dominated the road racing sector with the mighty TZ750, and Harley-davidson on the flat tracks. Abrams continues, “I was involved with the whole project as we supplied a lot of the parts for all of them. Five of us individually built them. They were all built by different people. We talked a lot and we did a lot of the same things at the time. We built the race wheels here for all five bikes. There’s a guy in Los Angeles who has copied them now and built two or three more.” The five TZ750 flat track riders had to wait until the first mile event at Indianapolis, on Saturday, August 23, 1975. After a string of mechanical issues, defending champ Kenny
Roberts was trailing series leader Gary Scott, and was desperate for victory. Kel Carruthers was Roberts’ mechanic for many years, and recalls, “We built the bike for Kenny in my road race shop using one of our spare stock engines. Indy was the first time Kenny saw the bike. We broke the footrest in practice and I made some mods before the semi and again before the main event.” Kenny Roberts recalls that first outing: “The first time I came out of turn four on the first lap, I moved on the handlebars to get some grip and the thing jumped into the air. And I damn near looped it! I thought ‘Holy shit’ this thing is going to hurt me if I don’t pay attention. From that point on I paid it a little bit more attention.
“If you rode it slowly it was no problem, it was a joy to ride. If you wanted to ride it fast there was a problem because the thing spun the tyres so easily. You made up a little bit of time on the straightaway and then everything would look good coming out on the back or front straight and then it’d just light up, and you were done. So that was the hard part, just getting it to hook up. “There was a kill button on the handlebar that killed one cylinder, but that didn’t work [for me],” Kenny laughs. “Normally I would pull my hand off the damned thing before I should have, and that would just put 30 more horsepower into it! So it would just whip sideways. Sometimes I’d use it and sometimes I wouldn’t, it didn’t really help that much. The TZ750 just wanted to spin the wheels as soon as you opened the throttle, so whether you had two cylinders or four cylinders, when you started opening the throttle it was still going to spin. “The problem was that the Harleys were doing about 30mph less – one time I went into turn one and Gary Scott and Mert Lawwill were racing each other and luckily Mert went to the outside. Had Mert stayed where he was when I pitched it in, I would have taken him out! And myself, or course.” Based on gearing and rev counter needle, KR said he was travelling faster than 145mph down the straights. “I actually split both of them going sideways about 30mph quicker. That was the downside of the whole thing – if somebody was in the way you weren’t going to miss them." But that’s not all King Kenny learned that night. “I had to ride the semi and that’s
when I decided I would shift it (change gear). Because when we shifted, it would pause just enough to get a little grip. I spoke with Aksland [Skip], he was third in his heat race and made the main event, I said, ‘Skip, you need to shift it.’ He said, ‘No, no, mine works good.’ I passed him in the main event so I lapped him!” Kenny chuckles. He won the first of the two semis and qualified for the final. “So I tried that in the semi and I won, it put me last on the second row on the line. That is where I started.” In the final, Roberts came from dead last to make third position exiting the last corner, with expert Harley-davidson riders Corky Keener and Jay Springsteen ahead. KR again: “It was on the amount of grip and you couldn’t follow a Harley in the middle of a corner because it spun too much. So it was high, wide and handsome the whole night, and as soon as I got a berm built up next to the hay bales I started passing everybody. Until then I would pass them and they’d pass me back the next corner, so then I’d pass them on the next straight. By the time I got to the mid-pack I’d started to build a berm. It was clear on the outside because nobody but me was riding there, and that’s how I was able to start passing people, and better people. “I thought I got third. For some reason I had a great hook-up – I don’t know how, as the tyre was half there as it’d chunked most of it off, luckily it didn’t go flat. I had hay bale wire on it from tapping the hay bales, so I came off that corner and I thought, ‘Man, I’m going to get third.’ Then I grabbed a gear, fifth, and went, ‘Wow, s*** I’m going to get second!’ I damned near hit Springsteen, I came on him so fast and so abrupt I swerved to miss him, I damn near hit him. Then I thought ‘There’s the start/finish line,’ – I won! “It was just the strangest thing, for some reason that last lap it just hooked up and I came off that last corner like it was a four-stroke.” Two weeks later the TZ750 flat tracker turned out to be useless at the Syracuse Mile, as the track conditions didn’t suit either TZ750 or Kawasakis H2R two-stroke due to wheelspin on the slippery hard surface. Few strokers made it past early practice – Roberts found he could lap two seconds quicker on his XT650/750 but, the less powerful Yamaha suffered yet another mechanical failure in the final. Roberts’ TZ750 flat tracker was altered after Syracuse, where it struggled on a surface more suited to the high-torque Harleys. Carruthers moved the engine forward and lower in the frame to help keep the front down. He turned the cylinder heads 180 degrees so the water hoses and couplings didn’t get in the way of the front downtubes. He then fitted road race wheels with hand-grooved ‘wet’ road race tyres, which later became the predecessor of the current flat track tyre design. In the end they didn’t help at the San Jose Mile due to constantly changing track conditions that went from wet to dry. KR had his XT650/750 and the TZ750 to choose from, and there was a lot on the line, as Gary Scott would struggle to get a top 10 at the upcoming Ontario road race.
KR went with the more powerful TZ after practicing on the twin, as did the other three TZ750 riders in attendance. Steve Barker went road racing that day. Remembering they had no time for testing, after a tank-slapping practice lap KR hit the wall and damaged his rear brake and footrest, which were found among the spectators and then re-welded. Despite the issues and being in pain, Roberts managed to qualify the bike in sixth position, behind H2R mounted Scott Brelsford. Each won a heat race to make the final, where three TZ750S, an XT650/750, and a pair of H2RS where pitted against 11 Harley-davidsons. But all eyes were on the Roberts vs Scott battle. Roberts had tried different lines looking for traction and race options but his soft tyres were chunking, forcing the team to risk an untried, hard compound slick with fewer grooves, but the big TZ simply spun its rear wheel in the final.
Chip Hennen was there. “You missed one of the most spectacular events you ever could have witnessed when these bikes were running, and this bike at the San Jose Mile with the H2RS, the ones that Erv Kanemoto built, it was spectacular, unbelievable! The stands were absolutely packed and everyone stood up at the start and they stood the entire race.” Roberts again: “After Syracuse we put 18in rain tyres on, and that’s what I used at San Jose, and I won the heat race. The problem was that it chunked the tyre. I had tested an intermediate cut slick in practice, when it was bare. I thought if the track blackens up, that cut slick is going to be miles better. In the main event the slick never hooked up, it was just the wrong compound, so it never got hot. Therefore it just spun all the time.” Roberts fought for control and dropped from a brief fourth early on with obvious tyre issues, he was 12th mid-race, and finally pulled out of the race altogether with Scott leading. “In the main event I thought ‘you poor bastards, you’re not going to see which way I went!’” Kenny says, still laughing. “And it was a disaster. They brought the black flag out just as I was pulling in.” The championship was over, and shortly afterwards so were the TZ750 and H2R flat trackers. Don Vesco still hadn’t built his TZ750 flat tracker by this stage. Some of the TZ750 flat tracker engines were removed, so the riders could use the motors in their road race TZS at Ontario, on October 5. Abrams reflects, “Hocking rode the Indy, Syracuse & San Jose Miles on the TZ750, however with no prior testing, Roberts was the only rider who put in top results. We only raced them for two or three races. Rick never set the world on fire on mytz750.”
Carruthers and Roberts were at the AMA rules committee meeting where the 20 members voted for a minimum piston displacement of 335cc, and maximum of two cylinders on either two or four-stroke engines. Carruthers says, “I voted to ban the bike. It was just one more bike some guys would need to run the series, but dirt track was mainly a Harley deal and it was just better to leave it as is. I think we did the right thing and left the series as it was. I believe if we had been able to build our own complete bike and with better tyres Kenny could have won all the Miles the next year. If we had run the bike the next season, Goodyear would have made the rain tyre in different compounds for us.” Roberts held the same opinion: “I voted to ban it. That wasn’t the right motorcycle for its time because it was going to kill someone, and I didn’t want that to be me! If you were to turn 10 of them loose on a racetrack, the guy who was probably going to get hit was me. I think had we not banned it, it would have won all the Miles with the technology of the tyres coming along, but at that time, with the tyres we had, they couldn’t have won the race.”
Above: KR just before his first ride – the Indy Mile. Mahony Photo Archives.
Right: Ken Roberts – TZ750 – Del Mar 1999, Mahony Photo Archives.
1 Ken Roberts,tz750; 62 Corky Keener; 42 Steve Morehead – San Jose Mile – Mahoney Photo Archives.
Kenny Roberts racing Yamaha XT650-750 flat tracker. Artwork. KR collection.
Above: The world’s most famous motorcycle engine, four-cylinder, two-stroke.t Stevenson Photo.
Left: Getting TZ750 down,t Stevenson Photo. Above: Four cylinders equals four wide air filters, which get in the way.t Stevenson Photo. Left: Kenny Roberts racing Yamaha TZ750 flat tracker. KR collection.
Above: Ray Abrams with his TZ750 flat tracker that KR demonstrated in 2009 and Rick Hocking rode in 1975. T Stevenson Photo.
Left: TZ750 flat tracker, rear end. T Stevenson Photo.
The bike KR rode at the Indy demo in 2009.T Stevenson Photo.
Left: Ray Abrams’ Yamaha TZ750 flat tracker engine. T Stevenson Photo.
Right: Montessa fuel tank from Kenny Roberts’ first flat tracker. T Stevenson Photo.
Above: Ray Abrams riding up the road.t Stevenson Photo.
Below: 1 Kenny Roberts,tz750 – San Jose Mile – Mahony Photo Archives.