[url=https://classicgoldwings.com/forum/viewtopic.php?p=212321#p212321:2ykyi2ef said:
marcusknight » Yesterday, 12:04 pm[/url]":2ykyi2ef]
...takes way too much squeezing to get any stopping pressure ... almost totally against the handle grip before it starts to do anything. ... if I squeeze it several times in rapid succession, it will build up more pressure, and require a little less squeezing then....a local shop replaced or rebuilt the master cylinder parts. But that didn't do much if anything. Bleeding did nothing.
Having to pump the brakes to build pressure is a clear indication that the master cylinder is not moving enough fluid to act on the caliper... but wait...
The master cylinder's volume doesn't just 'change'.
That means, something else has... and there's really only two parts left: the caliper, and the lines going to the caliper.
The caliper doesn't arbitrarily change volume, either. It CAN retract... and it will... if something PUSHES it back... like a warped rotor, or a caliper bracket that's flexing under load. It's not common on a well-built system, but if the caliper's suspension is bound up, or there's slack in the wheel bearings, etc., it can push the piston back into the caliper body, hence, it'll take several cycles of the master to push it back into contact with the disk.
The hoses SHOULDN'T arbitrarily change volume, either, but something I noted to my airbrake students in all my classes, is that a hose is really just a tank that's been made really skinny, and really long. In the case of hydraulics, a small-ID line will have a pressure-capacity advantage over a large ID, because the large ID has more internal surface to yield greater wall tension, in brake systems, the ID is small for that purpose, and a dozen other good reasons... one being that a small ID line can be made to fit through all sorts of tight spots using bent metallic tubing...
But braking systems work under high pressures, practically always need a flexible section to allow for suspension travel. The downside of a flexible line, is that no matter how new it is, it will ALWAYS expand slightly under pressure... and as they age, they tend to be a bit less strong, hence, they expand more... and the brake feel gets really mushy.
I believe this to be your most likely issue...
But I wouldn't recommend just changing the line. I would pull ALL the calipers, flush and rebuild them, flush out the master cylinders and hard lines, and replace all the flexible lines. After that, you should be excellent for another 30 years.
BTW... Don't believe what the 'good books' tell you: PLUMBING is the root of all evil. :rant:
