Do you have a timing light.
Yes. What kind of ignition do you have?
Here's a 5twins how too.
http://xs650temp.proboards.com/index.cgi?board=ID&action=display&thread=7984
The way you are doing it the light lead needs to be on the + battery post not the ground post, it will light when the points close (ground).
Timing will be when the light goes OFF (points open)