pleease help

Have a multimeter? Check the voltage from the voltage regulator.
Circled in red below.
4tttfp.jpg
 
Well if the voltage coming out of the regulator is out of the normal range, it should be replaced. If it is putting out the right voltage you should check the voltage coming from the light switch on the handlebars.

I'll be out for a while, but I'll check back in later.