small bubbles in brake fluid

I've bled the brakes on my gpz11 uni about 5 times and never been happy with the brake lever feel - always felt a bit spongey indicating air in the system. It has braided lines and serviced calipers. And didn't seem to be getting any bubbles out of the bleed nipples.

The braking system on this bike has about 6 bleed points, plus a splitter so they're a nightmare trying to get all the air out. Tried tying the lever overnight but didn't make much of a difference.

I read about a technigue of pulling the brake lever softly and letting it whap back loads of times with the MC cap off.

Tried it but couldn't see anything anything coming out of the supply hole - until I shone a torch through the site glass. There was a mass of microscopic air froth and tiny bubbles you could only see with the torch light every time the lever whapped back.

Even though tiny, I would imagine loads of them would cause the spongyness. I was at it for 15 mins and they were still coming out. Some were bigger than others.

I've done it a couple of times now and tapping the lines with a plastic handle and the lever feel has firmed up remarkably - I can now brake hard without trapping my fingers.

The rapid whapping seems to let the bubbles rise easier and escape. Worked for me.
 

Yup. Patuience and persistence are key ingredients when bleeding a complex system like that.

Did you use K&L brake caliper piston seals?

Nessism. no mate they were from brakecrafters. Can't see any leaks on the seals and they had new pistons fitted too.

I think it was air trapped in the splitter on the bottom yolk that just wouldn't move down when bleeding.

The whole system is a right pain to bleed.

I REBUILD MY VINTAGE KAWASAKI   AND NOW IT'S TIME FOR THE FRONT BRAKE LINE   
THE BUBBLE IS DUE TO THE BRAKE FLUID STICK ON THE HOSE OR OTHER PARTS ON THE BRAKE
FOR RESULT THIS PROBLEM   YOU NEED TO CHANGE SOMES PARTS   HOSE, BANJO BOLT OR CYLYNDER MASTER PISTON