back story: my '05 brake lever was a bit grabby, not because of bleeding but old age and gunk. i bought a used master off ebay, mounted and bled, seemed to be good. bike sat over winter and i came out to a pool of brake fluid on the floor however reservoir looked full. tightened all bolts, re bleed, no pressure. installed original master, no pressure. disassembled both old and new masters, intermingled parts, still no pressure. tonight i installed new master rebuild kit, still no pressure. the master will not seem to suck fluid in even when i place my thumb directly over the master's hole and try to build pressure that way. its the same behavior with the original and replacement reservoir. it gurgles air and a small amount of fluid comes but will not build pressure. i can pump the lever 100's of times but the fluid level never drops. what in the heck am i missing? ive replaced brake lines multiple times on different bikes and have never had problems pushing the air out.
problem resolved. bought a cheapo brake vacuum then pumping the brake lever about 1 million times. now i wait to see if it maintains pressure.
check with your dealer. suzuki has a huge recall on brake master cylinders. It may be covered and you can get a brand new one for free.
Masters dont pump air, as youve found out you need to bleed master b4 trying anything else. Can be a bitch.
that cheap brake bleeder from harbor freight works really well. bike master makes on also. they're about the same price. but I frigging love this thing. it works great. it will bleed the system in 2 seconds lol https://bikemaster.com/1-liter-pneumatic-brake-fluid-bleeder.html
