buy some brass plugs at your parts house & plug the M/C & if it is good(and bled) the pedal will be rock hard & virtually no travel. then take out (1) brass plug & hook up the line to the port next to the firewall & bleed them(your front discs) out & see what you get(for fluid and travel) and if it's the same then take off the 2 lines for the front brakes at the prop valve & plug the 2 ports on the prop valve w brass plugs & this will tell you if the prob is in the prop valve or downstream in the front calipers. EDIT on prop valves w the pin dont you have to pull it out(or in) to bleed the fronts?