Before my very recent engine troubles I re-did my front brakes in my CB750K.
I drilled out the rotor, sanded it with 80 - 120 -220 grit sand paper in my random orbit sander to de-glaze it and remove cross drilling burrs, dis-assembled and lubed the brake parts, bled the lines, and put in fresh DOT 3.
My brakes sucked when I left my driveway.
I did a couple dozen hard braking routines on a deserted road. Goose it up to 40 and squeeze on the brakes hard. By the end the bike was stopping faster than it ever had for me. I don't think I could do a stoppie, but I could hear the front tire squealing a bit in protest. It felt great to have a competent front braking system.
If you do this and your brakes still feel weak and spongy you may have a little air in your brake line which would require further bleeding.
Best of luck.