Suzuki goes large
The year 1971 saw the British ACU (Auto Cycle Union) and its opposite number the AMA (American Motorcyclist Association) in discussion as to how to grow track racing. GP bikes maxed out at 500ccs and endurance racing machine were limited to 1000. Theres was a woolly consensus that commercially produced machines should be given a racing class all of their own. The thinking was that it would be for bike racing in general, swelling tickets and also, hopefully, drive up retail sales.
What became the F750 would pull in BSA/Triumph with their push-rod triples, Honda’s CB750/4, Norton’s ageing Commando, Ducati’s V twin, along with Suzuki’s GT750 watercooled triple.
All machines were supposed to be based directly upon series production machines and it was hoped the old adage – race on Sunday, sell on Monday – would work.
Suzuki’s TR750, aka XR11, was a direct descendant of a production engine that had its roots going back to the last days of the 1960s and was the logical successor to the
XR05 we’ve covered previously. The development of the TR750 essentially saw the production engine taken off the assembly line and tuned along conventional principles such as increased compression ratios, widened and raised ports, along with a set of suitable expansion chambers. Thankfully, the rules allowed alternative frames and/or derivations of the road bikes’– the GT750’s chassis would never have been up to the job.
Over the first season (1972) bikes earnt the sobriquet Flexi Flyer due to their wayward handling.
Gradually the bike’s manners were marginally tamed with frame bracing and suspension upgrades, but the engine’s 100bhp always seemed ahead of the chassis.
By 1973 the motor was delivering a reliable 107bhp, thanks to revised porting and exhausts along with some seriously thirsty VM38SS carburettors. Unusually for a Japanese race team, Suzuki’s technicians and top racing brass listened to the Western riders regarding handling characteristics. Additional bracing, tubing and gusseting were added and both the strength and diameter of the steel tubes was increased – the upgrades worked reasonably well and amazingly, overall weight dropped by some 7kg.
That the bike was one of the fastest out there was never in doubt, but to underline its abilities Art Baumann qualified for the 1972 Daytona 200 with a measured top speed of 171mph on the straights. This was some 30mph faster than any of the fourstroke twins or triples. By the end of its working life the big TR was laying down 120bhp and attaining speeds of over 180mph on some tracks; unquestionably a huge achievement when the base GT750 was only rated at 67bhp!
The list of riders who met with success on the water-cooled works triples reads like a who’s who of early 1970s racers: Stan Woods, Jack Finlay,
John Newbold, Jody Nickolas, Tepi Lansivouri, Percy Tate and, of course, Barry Sheene, whose legendary crash on the Daytona cemented his reputation in the minds of race fans around the world. The crash is attributed to the bike’s rear tyre overheating causing delamination, but the accident was symptomatic of the new generation of racing machines. The power of the XR11 was capable of not only devastating the then current tyre know-how, but also overwhelming clutches, drive chains, ignitions and chassis construction.
By the mid-1970s Suzuki was focusing on the 500 GP world title, and Superbike racing marginalised the F750 series, but XR11/TR750 wasn’t ready to roll over and play dead. Specialist chassis builders such as Nico Bakker, Colin Seeley, the Harris brothers and others kept the legend alive.
When key data such as port and exhaust system dimensions became general knowledge. many enthusiasts converted road-going GT750s into XR11/TR750 analogues for both highway and track use – if that’s not a fitting tribute to a race bike then what is?
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