Have you tried a suction bleeder on the calipers. I've got a mityvac.
On my RD400, I had my master cylinder fitted with a stainless liner. I can't remember if I did the same on my NSR. All my calipers and master cylinders have had cerakote refinishing as well. It's brake fluid resistant and looks much better.
If the caliper seals weren't damaged when they were fitted and the hoses are securely fitted, then the only thing left is the master cylinder. It's a fairly easy job.
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