1980 KZ750 LTD H - Help filling brake lines after rebuiling calipers

Hey All,
I've been working on a garage kept but not run in a long time (like 10 years) bike. I pulled off both front and back master cylinder, 3 calipers and brake lines. Cleaned everything replaced seals and boots on calipers and reinstalled. I cannot for the life of me get brake fluid to fill the lines. I bought a vacuum kit and still can't get fluid to flow from the master cylinder through. I crank it to about 20 or 25, crack the bleeder a bit and I see some bubbling in the clear hose but that's about it. I didn't replace the brake lines but cleaned the hell out of them and tested them for air flow using my compressor. After a couple of days of dealing with this, I'm at my wits end. Besides buying new mc's and lines and calipers any and all advice is appreciated. Thanks in advance.

Did you put the MC cup seals into the right orientation!

This is the wrong:



This right:

Thanks for the pics and reply, yes I have the pri and sec cups opening towards the spring.

Both master cylinders have two passageways between the reservoir and the cylinder itself. One hole is easy to see, the other one is really small and easy to overlook. If the small one is clogged, you will have a heck of a time bleeding the system. A small e string from a guitar may be small enough to clear the passage.

That did it. Clearing out the small hole it had something jammed. THANKS!