My 1970 Harley XLH Sportster isn't charging but the generator and regulator are working what are some other common problems?

Mine did that for a long time... check the integrity of all wiring involved in the charging system. I had a grounding issue, replaced the wire and have been ripping ever since. Also, I don't know if you are aware or not to keep the rpm's up a little bit. If your idle speed is too slow in traffic and what have ya the thing ain't gonna charge........