Some of these gears are particularly hard to see, so start by clearing out the enemies of the level. Once it's safe to go hunting for them, follow the path in this video.
(Not mine)
Gear Locations -
1. Behind the first whirlwind
2. In the corner of the second room, make a right upon entering and look next to the first green pipe.
3. On a wall outside of a building (You will have to access it by taking the supercharge ramp to the second floor and flying to that round platform in the middle of the harbor. When you land, look straight out at the building you're facing and you should see it)
4. Inside the room with the pink grates, you'll find the next gear just left of the entrance
5. On the ground just under the doorway of the exit of that same pink-tinted room
6. Near the exit portal behind the first pillar to the left