You will need a multi meter tool and check the continuity in the switch.

 

thanks for reply ! could you tel me wot reading I should get when do this ? do u no which color Wier's are for the start switch ?

 

You will need to disassemble the switch to see the color of the wires. You will check for continuity. That will tell you if the switch is working or not. Are the brake lights coming on when you pull the brake lever to start the unit?

 

ok will do that..I do t have back brake light (its broke) .but when I connect the front lights they don't work either they use to work

 

Most quads have a safety that is the same switch as the brake light switch. So if your brake light doesn't come on then you will never be able to start the quad.