I just picked up a 1999 Softail Standard with the single front disc. It does everything except stop! What brake pads are you using, and do they work better than H-D/ I don't care about longevity, just stopping power.

BTW: The bike has 14k miles, and everything in the brake system works fine.

 

If everything is working fine it should stop.
Lindel pads are best.Bleed the old fluid, should be done every 5 years anyway.

 

I got a bracket to adapt a 4 piston front brake off a 2000 up HD. It was around $50 an then I needed a longer brake line an that was around $50. I had a caliper laying around I got the rebuild kit for an rebuilt. the finished brake worked a lot better but looked kinda bulky. Wilwood makes a cost effective upgrade: https://www.summitracing.com/parts/w...gaAnoaEALw_wcB

here's what the conversion looked like.

 

For a 20 yr old bike I would start with new lines and rebuild kit for both master and caliper. Caliper is fairly easy to disassemble, clean and rebuild. The master cylinder is another story unless you have ventured there before get a professional to handle it for you.

 

if you decide to rebuild it there's lots of videos on youtube