Long before the RG Suzukis became so dominant in the 500-cc Grand Prix racing class, privateers, and the works teams, relied on machines based on the twin-cylinder GT500 (Titan)Suzuki--the works bikes being known as the XR03s, or TR500.

The XR03s were extensively modified from their street cousins and included water cooling. Typical modifications for the privateer's bikes included racing pistons, high compression heads, close ration gears, straight cut primary gears and 34 Mikuni race carburetors.

The bike featured here belongs to Dutchman Cor Geraets and is a much modified 1969 T500 Suzuki. Cor purchased the bike from a friend in Holland with the intention of making it into a racer: "I always wanted to race motorcycles, it was one of two ambitions I have had, the other was music. Having done that, it was time to go racing."

Needless to say, the bike needed endless amounts of time to turn it into the competitive racer it is today, as it had been stored in a field for more than ten years!

For Cor, the project has required a steep learning curve in motorcycle restoration, riding, and even research. Finding the history of limited production machines can be a daunting task, Cor's determination eventually paid off to the extent that he has not only made a nice racer for himself, he has produced another eight bikes for customers. Making additional bikes and parts (particularly expansion chambers) is a side business from his main job as a contractor for Raben Technics—a Dutch subcontracting company specializing in special projects.

"The business generates sufficient profits to finance my racing with the Suzuki."

T500

After a complete restoration, the bike has been steadily modified over a 14-year period. Particular attention has been given to the engine which had been open to the elements and was full of water (not the best starting point for a racer!). The crankshaft was rebuilt using stock Suzuki rods and bearings. Stock Suzuki pistons are also used in favor of race versions as Cor found that, although the race pistons would let the bike rev higher, the stock pistons develop good power from 4,000 rpm up to a red line of 8750 rpm and are more reliable. The race versions increase the maximum rpm to 9500, but this stresses the crank etc. (Note: The early street bike - the Cobra - had problems with its pistons. A number of riders fit the GT750 pistons which are stronger.)

Cor changed the cylinder porting considerably by increasing the inlet period, opening the transfer ports (and matching them to the crankcases). He also lifted the exhaust port. The cylinder head was machined to increase the compression ratio from the stock 6.6:1 to 7.0:1.

On the Dyno 

The stock 32-mm carbs have been replaced with Mikuni VM38s. The 16% bigger carbs use a 360 main jet which speaks volumes for the state of tune on Cor's bike, a point that was proven when Cor had the bike on a dynamometer and found the Suzuki produced some 68 hp at the rear wheel!

With this much extra power (the stock bike has around 45 hp), the weak link in the engine/transmission became the clutch. To overcome this problem, Cor turned to a close friend who modified a stock clutch into a dry unit--not an easy task, but essential to stop slip under power.

Cor believes the current engine configuration is about at its limit of development and is working on a water cooled set up which, combined with a frame from an RG500, should make an exceptionally fast example of a classic racer, and that is not to say the current bike is a slouch. Cor's best results were at the Nürburgring in Germany where he has finished 2nd and 3rd in classic races. But perhaps the best comment about the competitiveness of Cor's bikes came from none other than former works Suzuki rider Paul Smart who observed to Cor "Man, your bikes are fast."

In addition to the 500-cc Suzuki, Cor has also converted a street GT750 into a TR replica. However, when it comes to riding the two machines, Cor tends to prefer the smaller bike which he says is "smoother and more rideable than the 750."

Note:

Replicas of Cor's bike cost between 12,000 and 15,000 Euros (which is about $8,760 to $10,950) and are available. Contact info can be found on his web site Samracing (named after his son Sam).