I apologise in advance for this long thread. I just wanted to lay out all the facts. I've struggled with this problem for quite some time and am really stuck so any good advice is welcome.

Bike: 1986 Blue/White GSX-R1100G. Excellent original condition. 30,000km's.

Equipment:
OEM brake master cylinders
OEM brake calipers
New Piston/seal kits installed
New Wezmoto braided brake lines (direct OEM replacements)
Castrol 5.1 Brake Fluid


I recently refurbished the brakes on my 86 1100. New pistons, seals and lines. Along with seal kits for the master cylinders and fresh gold caliper paint. As I'm sure is typical with these older bikes the brakes were in shocking condition.

I replaced the stock rubber hoses with Wezmoto braided stainless lines and went with the 3-piece front lines to mimic the originals, retaining the oem 1 into 2 brake hose splitter.

Now here's my problem...

No matter what method I use I simply cannot rid the front brake lines of all the air.

Method 1 - Bleed from the top down using a Mityvac.

Method 2 - After Teflon taping the bleed nipples to seal them I pumped the brake fluid from the calipers up to the master cylinder using a large syringe.

With both methods I used a large amount of brake fluid to ensure all the air was gone from the system.

No matter what, air remains.

Next step - After each bleed there is still air in the system. This residual air can be bled off patiently by gently pulling the brake lever allowing the air up at the master cylinder to be released out of one of the two little feeder/bleed holes at the bottom of the fluid bowl. By letting the brake lever "flick" back out each time seems to draw those remaining air bubbles out of the small bleed hole in the master cylinder bowl.

At this point the brakes are starting to develop at least an amount of pressure.

Next step - Once the brakes have built up some pressure (indicating most air is gone) I then rest the bike on the side stand and get it to a point that those little holes in the master cylinder fluid bowl are at the highest point. I then pull the brake lever into the bar (or as close to) and hold it there using a set of spring clamps. Leaving the bike overnight tends to let the last few air bubbles to slowly travel up the lines and out those holes. This firms up the brake feel a little more.

THE ISSUE - Even after all of this the brakes still have an unacceptable level of spongeyness.

POSSIBLE OPTIONS

Replace the new 3-piece "1 into 2" front brake lines with simpler 2-piece lines that run all the way from the master cylinder to the calipers, eliminating the oem splitter. Which could possibly be an air bubble trap.

Replace the master cylinder with a more modern one. I have read here on the forum of others using radial master cylinder from later model GSX-R750's.

HELP REQUIRED

Can anyone comment of the issues I'm experiencing?

Has anybody got any experience or advice on what I can replace the oem front master cylinder with?

The bike is in great original condition with on 30,000 Km's on the clock and I want to keep it as original as possible , but still ensure I have the best possible brakes. A front end replacement is not on the cards because of my wanting to keep the bike original.