While looking for something else, I found those old posts which I'm copying here in order to have it all "under the same roof" . Nothing sensationally new of course, but two well informed posts by Nigel and Glenn - I should have looked when I first opened this thread ....
QUOTE (Milan Fistonic @ Aug 3 2002, 07:44)

This was published in the December 14, 1973 edition of Motoraction.
Motorcycle Record Holder to Contest Stuyvesant Series
Motor cycle Land Speed record holder and U.S. Motor Cycle Champion, Cal Rayborn, has announced that he will be contesting the coming Peter Stuyvesant $100,000 Motor Race Series.
Rayborn, who has over the past years established himself as probably the world's most versatile and successful motor cycle road race rider, is now going motor racing in a big way.
His recent motor cycling history includes two wins at Daytona (1968-69). He travelled to Britain in 1972 to contest the Trans-Atlantic races winning three and finishing second in the remaining three.
For his exploits on road circuits, one mile dirt tracks and his 265 mile an hour land speed record for motor cycles, Cal Rayborn was voted the coveted "Rider of the Year" for 1973 by the U.S. publication "Cycle Magazine".
In 1968 Rayborn turned his hand to car racing, driving a Chevrolet Transam Camaro. With this car he took a number of top placings in U.S. regional and international events.
For the coming Stuyvesant series, Rayborn will be driving a Lola 5000 car which has been modified at considerable cost by Dan Gurney.
Over the past few months the car and engine have been completely rebuilt. A second engine has just been completed and tested as a spare, ready for the first race at Levin.
For several years a works rider for the Harley Davidson Company, Rayborn is expected to compete in a couple of selected motor cycle meetings, providing they do not conflict with his car racing efforts.
QUOTE (LamboNZ @ Sep 19 2008, 15:34)

Yeah the Suzuki T500, apparently his father-in-law who was mechanicing for him at the time, decided after practice that he wasn't going fast enough. The bike was derived from a road going engine, and part of the mods was to put a polyester filler in some of the ports, so his father-in-law took it upon himself to run the bike on alcohol, which had never been tested.
In the race, just starting the second lap, the filler had deteriated and come loose, causing too much air and leaning the mix off too much and seizing the engine. This resulted in Cal tragically having a high speed colision with the barriers at the first turn. (Dec 29th 1973 RIP)
QUOTE (GD66 @ Sep 20 2008, 14:59)

Yes, I can confirm that this happened in the first race heat, at the end of lap 1. Cal had been set to race a Lola T190 in the Tasman Series for F5000 cars, and the Suzuki ride in the Marlboro Series, on a Colemans TR500 twin, came about as he'd been signed to race for Suzuki in the AMA series the following year, having been working his butt off on the Harleys for years against the rising tide of Japanese two-stroke opposition. It's my impression that he'd also made a conscious decision to specialise in roadracing rather than pursue the Grand National tour, as his results on the Harley against Ray Pickrell and the lads in the Transatlantic had confirmed his belief in his tarmac skills. Anyway, through a convoluted set of somewhat tenuous circumstances, he was a starter at Pukekohe on the Colemans TR500, and for sure the bike was converted to alcohol on the day. His father-in-law was chief mechanic, in company with Colemans rep Joe Lett, and Len Perry. At the end of lap 1, when he crossed the start-finish line and sat up to dip into Champion Curve, the bike seized, and the back stepped out wildly, straightened briefly, then stepped out again, spat him off the left side and chased him into the armco barriers, which he hit sitting down and sliding backwards, and then ricocheted back onto the track. The race was stopped immediately, but having seen all this directly in front of me and already fearing the worst for one of my heroes, my fears were ramped up by the repeated calls for anyone on the course who may be a doctor to please assist at the ambulance station.
Looking back now, I doubt whether poor Cal could have been saved even if a doctor had been on hand, but as seconds drew into minutes and time went agonisingly by, the pall of dread spread pervasively through the crowd, and somehow we all knew that this was a bad one. Without question, it raised the inadequacies of the medical facilities in those times, but it was a cruel blow that was felt worldwide in the roadrace community, and it all seemed so needless....