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Sound of Thunder
BEARS Rules and Regulations

BEARS Supplementary regulations

Motorcycles must be of British, European, or American design with an engine and chassis of non-Asian design or manufacture. MACHINE ELIGIBILITY for any class is at the discretion of the race committee. Ensure your machine complies with class rules.

ALCOHOL FUEL. BEARS 4 stroke machines may use alcohol fuel. Any machine using Alcohol fuel must display “Dangerous Goods” or other appropriate stickers which clearly indicate its use, on the machine in a prominent place and on storage containers (MNZ rule 10.21b).


All machines must comply with all safety requirements as specified in the MNZ manual of motorsport. (MNZ rule 10.1)

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Official BEARS Classes

  • BEARS Formula One: Purpose built race bikes and technically advanced production sport bikes. 661cc - Open capacity, fuel, and tyres. No cross entry between F1 and Formula Sport.

  • BEARS Formula Sport: Pre 2006 production based sport bikes 550cc – Open capacity. Purpose built race bikes and post 2006 machines 550 – 660cc. Pump fuel, Open tyres. No cross entry between Formula Sport and F1.

  • BEARS Formula Two: Purpose built race bikes and production sport bikes: Four stroke, 350 - 805cc multi. Max. 2 valves per cylinder - Pump fuel, Open tyres. 350 - Open single - Open fuel, Open tyres. Two stroke, 0-350cc multi. 0 - 600cc single - Pump fuel, Open tyres.

  • BEARS Superstock: Production based bikes. Original engine chassis & suspension layout. Modifications are permitted providing original concept and design are retained. E.g. a twin shock suspension may be altered to a box section swing arm but not changed to mono shock etc. Pump fuel only. Open Tyres. Two classes:

    • 0 - 750cc fuel injection allowed if fitted as std equipment. Four stroke multi Max. 2 valves per cylinder. Single cylinder machines may have 4 valves per cylinder.

    • 751 - Open cc fuel injection allowed if fitted as std equipment. Four stroke multi Max 2 valves per cylinder. Single and shaft drive machines may have 4 valves per cylinder but multi limited to 1000cc.

  • Heritage: Any tubular steel construction frame with non upside down forks, must have twin rear shock suspension, one mounted each side of rear swing arm. Shaft driven bikes with twin or single shock must have rear shock absorber mounted beside differential. Open tyres, open capacity engine, air cooled, open fuel, carburetted and non- belt driven valve gear.

  • Lightweight: Two classes run concurrently. Open fuel, open tyres. No GP bikes.

    • Lightweight Ltd - Four Stroke, 0 – 400cc singles and air-cooled multi’s -Two Stroke, 0 – 350cc air cooled singles, 0 – 250cc air cooled, Multi’s and water cooled singles, 0 - 125cc water cooled multi’s.

    • Lightweight: Four Stroke, 401 – 600cc singles & air cooled multi’s, - Two Stroke, 351 – 400cc air cooled singles, 251 – 300cc Water cooled singles, 251 – 400cc air cooled multi’s, 126 -200cc water cooled multi’s.

  • Moto-Euro: Any bike manufactured in mainland Europe. (i.e. no British bikes) European engine and frame or frame of non Asian design. 401cc – Open water cooled 4 valves per cylinder twins. 601cc – open capacity all other machines. Open fuel, Open tyres.

  • Best of British: Open to any motorcycle manufactured in Britain. British engine and frame or frame of non Asian design. Open fuel, open tyres. Four classes run concurrently:

    • 0-750cc

    • 751cc-Open

    • Hinckley Twins

    • Hinckley Triples and Fours.

  • BEARS Classics: (Non Championship Class) Non Asian design, pre 1972, no disc brakes, treaded tyres. Frame and suspension must resemble this era. Two classes run concurrently:

    • 0 - 500cc

    • 501cc - Open.

  • Milwaukee Iron: Open to any Harley Davidson, Buell or EBR. Frames must be of non- Asian design. Open Fuel, open tyres. Two classes run concurrently:

    • 2V (max 2 valves per cylinder)

    • 4V (max 4 valves per cylinder).

  • BEARS Novice: (Non Champions class) Eligibility of rider & machine subject to Clerk of Course or Race Committees’ approval. Non monetary prizes. To be run concurrently with BEARS lightweight class. If the Novice class riders have done less than 5 events, they MUST wear a fluro vest to identify this to other riders.


As per MNZ direction, races to be limited to 50 bikes on the starting grid per race.

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