500 Air Cooled Mod / Stock Liquid Cooled 500
Mod air cooled engines / stock liquid engines. 500 cc max.
  1. 500 cc max
  2. Air cooled engines may have any aftermarket exhaust system
  3. Liquid cooled engines must run their stock unmodified single pipe exhaust system.
  4. Leaf sprung chassis 1985 and older may compete.
  5. Any drive or driven clutch
  6. No EFI / must be naturally aspirated engines.
  7. Any carb allowed
  8. Engine brand must match chassis brand.
  9. Any track, 1 inch lug max
  10. Studding allowed, 3/8 max above track lug.
  11. Carbides allowed.
  12. Any internal or external engine modifications allowed on air cooled engines.
  13. No internal or external modifications on liquid engines.
  14. Any chaincase, any gears, any sprocket size
  15. Skis may be any commercially available steel, plastic or aluminum ski of leaf spring design. Springs must be steel and functional.
  16. Brakes may be upgraded and the location may be moved, shielding must be in place if disc is moved to the driveshaft.