head lite on the dim side

more gobblins as halloween nears i guess..my head lite is bright on high beam but is very dim on low beam. when i rev up the bike then the low beam gets brighter like its on a magneto bike...has anyone ever had this problem?,,,tia    1979 kz1000ltd  all stock
 

What is the battery voltage with the engine running and what is the voltage at the bulb connector with it connected and working 

ok ill start looking there first
 

Sounds exactly like what happened to my gpz550. The low beam of the dual-filanent h4(?) bulb had gone bad and needed to be replaced. I dont know if you have the semi-sealed headlight, but if you do, take the bulb out and inspect the windings for the low beam. The one on my gpz550 had become all frayed. If the bulb is fine then wookie can probably help you more than I can.