Tailight but no brakelight on 83 honda 550?

I have a 1983 honda nighthawk 550. The brakelight works fine but there's no tailight. And the tailight light is on, on the instrument panel. How can i fix this? Is it a fuse?

Didja check, like, the bulb, dude?

Check the circuit with a test light or multimeter.

Simple as that. Start at the light switch and work out to the light, or go from the light back to the switch.

Two filaments in one bulb.

Remove the rear light lens.
Take out the bulb.
Hold it up to the light.
You'll see two filaments - one for the tail-light and one for the brake light.
The filament for the tail-light will almost certainly be broken.
Buy a new bulb, fit it and replace the lens.

Replace the tail light/brake light bulb.