About Australian Thunderbikes :
A 'thunderbike' is any solo motorcycle which has an air cooled four stroke motor with fewer than four cylinders and with two valves per cylinder.
This definition should be used to establish road racing classes for this particular type of machine.
The Australian Thunderbike Association has been established to encourage racing of these types of machines in capacity classes regardless of year of manufacture, as well as in common 'historic' events, and BEARS racing. Maintenance of machine authenticity is encouraged, in particular attention to detail of old machines which have a racing history. Modern machines and retros which fit the criteria, are welcome to compete in the proposed race classes.
NOTE : Two stroke, as well as four cylinder engined machines are specifically excluded from all thunderbike race classes.
Typical Australian Thunderbikes:
Vincent 1400 Retro
Ducati 250
Norton Manx 500
Norton Atlas 750
Ducati 900
Norton Commando 750
Triumph 750
Laverda 750 SFC
Seeley Norton 850
Ducati 900
Norton Vincent 1000
Vincent 1000
Ducati 600 Pantah