Unlock all tracks:
At the mode selection screen, press Up, Left, Right, L, Z, R.
Unlock all bikes:
At the mode selection screen, press Up, Left, Right, L, Z, R, Up, Down, Down, Z, Down.
Get the best selection of
Top Gear: Hyperbike Cheats, Codes & Walkthrough/Guide/FAQ for Nintendo 64 from Cheat Code Central
The Genie has more
Top Gear: Hyperbike Cheats at CheatingDome.com.