Your Rotom Bike can be upgraded to significantly improve Wild Area traversal. Initially, you'll get a speed boost. Later, after defeating the sixth Gym Leader, you'll receive an upgrade that allows your bike to travel across water. This opens up new areas of the Wild Area and makes reaching certain Pokémon Dens much easier. To get the water upgrade, speak to the man near the bridge in Route 9 after getting your sixth badge. Further speed upgrades can be purchased from Watt Traders.
