Mach Bike is an item in the “Gameplay” category (Key Items).
In-game descriptions
| Ruby / Sapphire | A folding bicycle that more than doubles foot speed. |
|---|---|
| Emerald | A folding bicycle that doubles your speed or better. |
| FireRed / LeafGreen | A folding bicycle that is at least twice as fast as walking. |
| Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! | This folding Bike more than doubles your movement speed. |
| Sword / Shield | This folding bike more than doubles your movement speed. |
Where to find it
Not placed on the atlas maps (so far: Red/Blue and Generation 3).
Sources : PokeAPI (items, item_flavor_text, machines) · atlas · pokeemerald species_info.h