Sintered pads last longer but require higher pressure to stop - take the pads out, wash them and the rotors in lacquer thinner, sand the rotors in a circular pattern with 80 grit emery cloth - sand the pads perpendicular to rotor rotation (inside to outside edges of the pads) - if the rotors are drilled, more pressure is required. The only way to increase pressure is to decrease the diameter of the master cylinder, increase the surface area of the caliper piston, change the fulcrum point of the brake lever or make the brake lever longer.
Note: organic (soft pads) stop with less pressure, wear quickly and are less efficient when wet - sintered pads last longer, are less affected when wet, require more pressure and are hard on rotors - rotors that have ridges worn into them effectively have 1 or 2% more surface area for better stopping ability - drilled rotors have less surface area, but run cooler and help carry water away from the pads, but the holes can fill with mud which is abrasive and will accelerate pad wear.
I think if you manage to get all the air out of the system the braking will be much better. Maybe flushing out the DOT 4 brake fluid and replacing it with DOT 5.1 might help also. Run the vehicle with the brakes slightly on until they are smoking hot and that will help cook out any residual oil and improve the feel also. In addition, getting the brake fluid to near it's boiling point or even boiling the fluid a bit will improve brake feel when it cools down because hot fluid will contain a lower % of water.
2006 Trailboss 330
2002 Sportsman 90
2005 TRX400EX (FOR SALE)
2003 LT-Z400 (needs engine work & is for sale)
1971 Triumph 650 Bonneville (has 5 original miles)
1972 Triumph 650 Bonneville (undergoing restoration)
1979 Honda CBX (6 cylinder)
1970 Kawasaki G3SS 90cc Bushmaster
1976 Suzuki RE5 Rotary (not running & FOR SALE)
1981 Kawasaki KZ305-A
1981 Suzuki GS450T (undergoing repair & will be for sale when done)
1982 Kawasaki KZ750-H (FOR SALE)
1989 Honda VT1100C
2007 Vectrix VCTX Electric Scooter
1965 Montgomery Ward 3 1/2 HP Tecumseh Mini Bike
1970 Triumph T25 250cc Trailblazer
1968 Triumph 250cc Flat Tracker
Shop Owner and Mechanic with over 50 years experience