the switchs play up on them ,does it have a lights on/off switch and a hi /low beam switch or just one ?they go green and manky inside and stop working,but as steo said check the bulbs first do the brake lights work ok on the grab rail? if not then the earth wire could be off or dirty at the back of the bike,they have seperate brake lights and tails lights on this model you see.
adam bike doctor, November 2009