When I replaced my original M/C with a power disc system (frame mounted), I used a vacuum bleeder, went thru over quart of fluid and still couldn’t get the air out of the system. It wasn’t until I had my wife come out to do it the old fashion way that I was able to find my leak. The vacuum only allowed air to be sucked in so there were no fluid leaks. The pressure from the M/C showed me the leak. Once I fixed that leak, the bubbles went away.
