The legend of Roberts and the TZ has jumped the shark. There were multi cylinders bikes on the mile well before the TZ700/750 ever showed up. BSA and Triumph had used the 3 cylinder motor in specialty framed trackers as soon as the rules allowed (1970). The TZ produced about 125 hp. Roberts wasn't pitching it sideways at 150 for sure. The rule change wasn't the reason the CB750 didn't succeed on the mile either. Like the 3 cylinder brits it was too wide. The motor had to sit high in the frame to keep it from grounding in the turns which made it handle poorly. The CB didn't have the low end power of the British and American twins either. Kel Carruthers (Roberts builder) spearheaded the move to ban the TZ from the mile. Roberts didn't destroy the competition at Indy 1975. He was at the rear and barely won on the final straight. He raced the bike two more times and didn't do very well. The TZ was a failure. If it wasn't banned it would have been abandoned just like the CB750 milers. The video of the Indy race has been pulled from youtube but it is funny to watch as KR goes wide in the turns. He was totally off the line and barely pulled out the victory.
Scott
You must not have been there... I was.
Roberts hadn't seen or ridden the bike before that Saturday night. He wasn't "off line" for a two stroke, he figured out the line as he rode, coming from a near last place start to pass Keener and Springsteen on the last straight. He wa riding hard enough to clip the bails coming out of the corners, because he could and he was going to win or break trying. As for pitching it in, he went in high, down low and came out high - classic two stroke technique.
(I saw Rick Hocking running a vintage TD1 Yamaha twin at Ashland Ohio doing the same thing and putting the nearest 750 a half lap down.) So I'd say "barely pulled out the victory" is quite an understatement. You had to be there to see what we saw... literally a come from behind win the first time on the bike.
Based on that I'd say your comment "Roberts didn't destroy the competition at Indy 1975. He was at the rear and barely won on the final straight." is the ultimate in downplaying what an incredible race it was. Virtually last to first - just what would he have had to do to destroy them? Wheelie past them at the line?
By the way, Roberts said exactly what has been quoted. But Roberts was all in favor of running 500s on the roadrace courses and flat tracks. One possible reason was that tires were not up to for the demand on them at that time.
I'd also like to note that the Triumph triples weren't all that bad on the mile tracks until the all-alloy XR750 came out. Jim Rice ran pretty well on them.
You could learn a lot if you could get ahold of a January 1976 Cycle World magazine and read the articles. That combination allowed a roadracer to have a mile bike for the cost of the rolling chassis, instead of having to buy a whole bike - roadracing paid AMA Grand National points back then, which helped Roberts a lot. Doug Schwerma of Champion frames, with no help from Yamaha, built up the bike to use as much of the roadracing parts as possible. The bikes were tested on regional tracks like Ascot.
The ban ended any possible development on any multis, so there was no testing of detuning, flywheels, and possible big bang crank set ups. It was gone and I'd say flat track has been far the worse for it - 38 years of domination by a single engine design
(Of course the AMA did it's job weighing down the Honda when it came in during the 1980s, effectively killing Honda's incentive to participate.) There were struggles in the Syracuse race where I believe Roberts got sixt and a bad tire choice took him out of contention at Sacramento later that year. The bike also brought the rain tread road race tires on the tracks by Roberts, which was the predecessor of the present flat track tire tread design.
Like I have said before, they either should have stopped it before it started or they should have let it as you say be "abandoned". Would they have worked eventually? Neither you nor I know, or ever will know. What a shame... Just like throwing all that lead on the bottom of the NS750. Kill it off if it beats the XR.
