My 1995 K1100LT with ABS started locking up the front brakes and the master cylinder began leaking so I had my mechanic install a Magura master cylinder rebuild kit from Beemer Boneyard and replaced both front and rear lines with a stainless steel lines kit from Spiegler Performance Products but can't seem to get the system to bleed. We tried "back bleeding" through the bleeder valves and still no pressure. What's the trick to resolving this issue?