You know that really cool motor bike sound? Have you ever wanted to have one for that sound but you don't have enough money? Look no farther. This is a very simple fix and an awesome sound.
Step 1: Supplies
What you will need:
A plastic water bottle
A bike with bumpy tires
Step 2: Assembly
Crush the bottle. Then shove it in between the tire and the top of the fork (look at the picture for better explanation).
Step 3: All Done!
Now ride around town and impress all your friends with your dirtbike!