Motorcycle Repair: Honda CT90, moving down the road, timing advance

Question
I recently purchased a 1974 CT90 to ride back and forth to school. The bike runs fine as long as I stay in the throttle and moving down the road. When I get to a stoplight and sit for a minute or so, as soon as I touch the throttle again the bike shuts off. If I keep it revved up in neutral and put it into gear when the light turns green it will usually go ahead and take off. However, if I just let the bike sit and idle the engine will begin to run slower and slower until it finally shuts off after about two or three minutes. Any suggestions?

Answer
Could be the idle air adjustment or possible low compression.  When it idles, does it idle at the right engine speed before it dies or does it idle at a elevated speed and then suddenly slow down and die? If it's the latter the timing advance unit could be worn out.

Regards
Rich