Your visor protects your eyes from wind, rain, insects and road dirt. It's therefore important to keep it clean and in good repair. A badly scratched visor can, obscure your view and cause dazzle from lights of oncoming vehicles.

Purchase a new visor that is designed to fit your helmet and follow the manufacturer's instructions for how to remove the old visor and replace it. 

If you need to clean your visor or goggles, only use warm soapy water, or special products designed for it. Don't use abrasives or household cleaners.