Grand Prix (Period I)

Grand Prix classes are limited to thoroughbred grand prix motorcycles, and race-prepared roadster motorcycles of comparable performance and appearance, with a maximum model year of 1967, with the following exceptions permitted regardless of model year:

  • Aermacchi / Harley Sprint 250 or 350 four stroke single through 1974
  • BMW through /5
  • BSA (all singles and twins)
  • Bultaco through 1972 (PROVIDED no cylinders, crankcases or cylinder heads later than 1967 style)
  • Ducati singles through 1974
  • Greeves Silverstone, Cotton Villiers
  • Harley-Davidson KR, ER, CR
  • CB/CL/CR 450 (torsion bar valve spring type head)
  • Jawa 2 valve, OHV, four stroke single cylinder speedway engines through 1978. NO original style total loss lubrication, period cycle parts required.
  • Kawasaki A1RA, A7R, A7RA
  • Later specialty frames (e.g. Seeley, Rickman, Yetman) with eligible engines
  • Norton Atlas, Commando
  • Royal Enfield
  • Suzuki T250, T350 & GT250 (Ram-Air removed)
  • Triumph (all singles and twins)
  • Velocette
NOTE: above "excepted" machines are still subject to general Grand Prix rules set forth below, irrespective of original equipment. Stock CB/CL 350 twins are no longer elligible in Period I GP. They may run in Formula-CB or modified CB/CL/CR 350s may run in Lightweight Supervintage

Classes based upon displacement:

  • 200 GP      up to 200cc
  • 250 GP      201cc through 250cc
  • 350 GP      251cc through 350cc
  • 500 GP      351 through 500cc
  • Open GP   501cc and over
Displacements above do not include permissible overbores of 5% over class limit

Rules applicable to Grand Prix Period I classes
i. Engine: air-cooled only (except for pre-1967 OEM). No pressurized induction. Internal updating permissible; external appearance should remain same.
ii. Gearbox: Internal updating permissible: external appearance should remain same.
iii. Wheels:  maximum width 2.5 inches (WM-4) Wire-spoked wheels, minimum 17-inch diameter,
iv. Tires: maximum width of 130mm (as stamped by manufacturer on tire). Treaded tires only: no slicks, or slicks treaded after manufacture.
v. Brakes: Drum only, irrespective of original equipment.
vi. Maximum fork tube diameter 35mm unless machine originally equipped from the factory with larger units.
vii. Swingarms must be 2-sided, of round steel tubing material, and have a shock absorber located on each side without secondary linkage (OEM excepted; e.g., Vincent and NSU). 
viii. Carburetors: round slide or period type only.

Table of Contents (click on any item to view that page)
Names and Addresses
Class Overview
Bumping
Rule Changes
Championship Points
General Rules
Early Vintage & Pre '65
Screaming 50's
Grand Prix (Period I)
Supervintage (Period II)
Middleweight (Period III)
Period IV
Formula RD
Formula CB350
Sidecars
American Twins

Last Updated: 2/25/06