Start by checking the connector direct on to the bulbs, then see if the bulb itself hasn't blown or the fuse under the seat, then there's a connector block underneath the tank, loosen the bolt for the tank under the seat but don't undo it, use this as a hinge, undo the bolt at the top of the tank by the handlebars and gently lift up the tank, don't lift it to fully vertical, just 6 inches or so and support it with a block of wood or similar, there's a black box (not the airplane kind cause they're bright orange/red) lift the lid on the box and check all connector blocks, possibly unplug and spray them with electrical contact cleaner or wd40
