I have a 1990 db1 just replaced battery and alternator but my battery light still comes on. I checked all connections and grounds no problems seen. Every time I turn on the lights it wants to die. Any ideas what it can be?

 

the battery light only turns on when there is inadequate charging voltage. measure the charging voltage with a multimeter. should be roughly 14-14.5 volts.
if the connections are all clean and tight, i'd probably measure resistance of the B+ cable. should be 0 ohms or close to it