Proposed Eligibility Rules (24th November 1999)
Post Classic Road Racing
Eligibility Rules
All machines in the post classic classes shall have full or handlebar fairing, racing tank and seat, and clip-on handlebars, and racing exhaust system, and shall have the appearance of a grand prix or endurance racing motorcycle, as distinct from a production racer.
All machines will have single spot disc or drum brakes only.
All machines will have cantilever or double shock suspension only, (rising rate suspension with linkages and single shock absorber is not permitted).
All frames shall be constructed of round section steel tube.
Minimum wheel diameter is 18 inches on all solo machines, magnesium wheels are permitted, any tyre size is permitted, slicks are not permitted.
Any year motorcycle is eligible, provided it complies with the other requirements of this document.
Use of alcohol fuels is permitted.
No capacity limit.
No limit on number of valves.
Aircooled motors only.
850 cc capacity limit.
Two valves per cylinder max.
Aircooled motors only.
750cc capacity limit.
No exhaust port control permitted.
Watercooling permitted on all machines.
Reed valves permitted.
750cc capacity limit
No limit on number of valves per cylinder.
Aircooled motors only.
600cc capacity limit.
Two valves per cylinder max.
Aircooled motors only.
2.3 Two Stroke Machines.
500cc Capacity limit
No exhaust port control permitted.
No four cylinder motors permitted.
Watercooled motors permitted on single cylinder machines only.
No reed valves permitted.
500cc capacity limit.
Aircooled motors only.
No limit on number of valves per cylinder.
400cc capacity limit.
Aircooled motors only.
Two valves per cylinder only.
250cc capacity limit.
No exhaust port control permitted.
Watercooled motors permitted on single cylinder machines only.
No reed valves permitted.
4. POST CLASSIC LIGHTWEIGHT
350cc capacity limit.
No limit on number of valves.
Aircooled motors only.
300cc capacity limit.
Two valves per cylinder only.
Aircooled motors only.
125cc capacity limit
Watercooled motors permitted on single cylinder machines only.
No reed valves or exhaust port control permitted.
Rationale
These eligibility rules are unfortunately complex. They are based on brake mean effective pressure (valve area and capacity) for various types of machine, to provide competitive classes similar to those of the post classic era.
The rules limit 3 and four cylinder machines to ‘two valve motors’, as the change to four valves per cylinder marked a major step forward in racing machines. Capacity for these machines has been limited in the interests of allowing twin cylinder four strokes to be competitive, and preventing use of 1300cc Kawasaki engines, which were not available in the era. This proposal is similar to that adopted in the 70’s Endurance Racing in Europe.
Exhaust port control in two strokes, is similarly prohibited as this improvement marked the end of the era.
The move to ‘forget forgotten era’, and allow watercooled Yamahas to compete in the ‘Unlimited’ class, should bring some reality to the competition.
There is a requirement for ‘racer appearance’, as most ‘sit-up’ machines were only used in C grade during this era. While it might be cheaper racing to exclude this provision, it also looks cheap.
The proposed eligibility rules for Post Classic Road Racing are based on four classes of machine raced from 1962 to 1979..
These rules do not specify year of manufacture for ‘eligible’ machines, however the prohibition on four valve per cylinder three and four cylinder machines, exhaust port control on two strokes, and rising rate suspension with linkages, along with specification of 18 inch minimum diameter wheels, and use of single spot calipers only, effectively sets the era and type of machine which is eligible.
The classes are ‘Unlimited’, ‘Senior’, ‘Junior’, and ‘Lightweight’.
The type of machine which would be competitive in ‘Unlimited’, would be 920cc Norton Twins, 1000cc Vincents, some later model Ducatis (although the wheel size would exclude many), the Trease Harley Davidson, Moto Guzzi Twins, Laverda Twins, 750cc Honda and Kawasaki fours, Triumph/ BSA Triples, and watercooled and reed valve model Yamaha two strokes and Kawasaki H2(R)s. (In this era water cooled Yamahas were the winners, however it is unlikely that anyone could seriously campaign a TZ750 these days, if they do – they deserve to win).
The type of machine which would be competitive in the ‘Senior’ would be 750cc Triumphs, and Nortons, four valve singles (some modern bikes), 500cc Honda and Kawasaki fours, 500cc air cooled Suzuki and Kawasaki two strokes, 350 and 250 cc Yamahas (air cooled) without reed valves (TR3 etc.)
The type of machine which would be competitive in the ‘Junior’ would be 500cc twin or single Nortons, Triumphs, Hondas, BSA, Ducatis, Yamaha etc, 350cc Honda Fours, 250cc and 125cc Bultaco, Yamaha and Suzuki two strokes.
The type of machine which would be competitive in the ‘Lightweight’ would be 350cc single cylinder British and Japanese machines such as SL350 Hondas, 7R AJS, 350cc Honda twins, 250cc Honda fours, and 125cc Two Strokes such as the TSS Bultaco, Bantam and Kawasaki and TA125 Yamahas.
An advantages of these rules are that they encompass a wider range of machines, while retaining the type which was raced in the post classic era. They include a form of handicapping which should improve competition. Lower capacity class machines can still compete in all higher classes, however the ‘Unlimited’ class should prove daunting to those from the ‘Lightweight’ class.
