
Thunderbikes is a generic term which refers to a class for aircooled single, twin and triple cylinder fourstroke engined racing motorcycles. Typical examples may be seen at:
http://www.youtube.com/watch?v=fbfcYf_aS4Y&feature=fvsr
These machines are raced in all MA historic periods, BEARS, and FX Pro Thunderbikes, in various capacity classes
Thunderbike Links
ThunderbikeUK
http://www.thunderbike.org.uk/index.php
FX Pro-Thunder Eligibility Rules