Fortunately, a motorcycle brake light is an easy thing to fix. Very few supplies are needed, and most riders have found they can do this repair in less than two hours. To start, you will need to purchase a new brake light bulb, a light cover (if the old one is cracked or missing), wire strippers, an electrical connector, needle nose pliers, a Philips head screwdriver, pliers, and electrical tape. You should be able to find all of these supplies at your local auto parts store.
Start by accessing the motorcycle brake light. In order to do this, start by loosening the cowl behind the seat. After lifting the seat, loosen and remove the nuts holding the cowl to the seat. At this point, you should be able to see and reach the back part of the brake light.
Use the Philips head screwdriver to remove the brake light cover. This will give you access to the bulb. Unscrew and remove the bulb. Look for the wires connecting to the lighting assembly. Since every bike is different, write down which wires are connected to which connector before unclipping them. To unclip these wires, use the wire strippers to cut the wires just behind the connectors. Discard these pieces of wire.
Next, use the wire strippers to remove about one inch of insulation from the end of the remaining wires. Push each bare wire into the connector, being careful to follow the original wiring of the light. Close each wire using the pliers, then seal the joint with electrical tape. Once all of the wires are securely in the connectors, push the connectors back into the brake light area.
Screw a new bulb into the fitting. Check to make sure the repair was done properly by turning on the brake light. If it works, fit the brake light cover on the fixture and screw it into place. Replace the cowl before riding the motorcycle.
If the brake light is still non-operational after checking all of these step, then you will probably need to take the bike to a mechanic who can check the wiring of the light fixture.