It is possible that your bearings are dirty or worn out. Use the [[Boosted Board 1st Generation Troubleshooting|Boosted Board 1st Generation Troubleshooting]] guide to help take off the rear wheels and replace the bearings if they are broken or worn out. You can check out this [http://www.instructables.com/id/Clean-and-Grease-your-Skateboard-Bearings/|Guide] to clean your bearings.