Front Brake Dragging

[bojangles]

Hello

New to XS650's and this forum. I recently purchased a 1980 XS650 that developed a dragging front brake. Previous owner installed a MikesXS master cylinder because the stock one was corroded and unusable. He noticed the brake began to drag after this and noted it could be a collapsed hose. I installed a new MikesXS caliper and it seems to have made an improvement but the brake still drags a bit less than before. Im about to buy new hoses from MikesXS and have a completely new kit
What is interesting is that I tried pushing the caliper piston in to fit pads and it would not move regardless of force (C clamp), unless I opened the bleeder on the caliper. Looking around the internet, it is showing this exact symptom is common for collapsed lines as fluid can get to the caliper, but not enough force to get back to the master cylinder.

Even though Im buying new hoses right now, anyone have thoughts on this?

Thanks
Bojangles

 

[gggGary]

Yeah I have pretty good idea, this has happened a bunch of times with imported MCs. There are two ports from the reservoir to the piston bore; the first one is big about 1/8" or so, the second "bleeder" port is tiny, really tiny, like the smallest drill in a machinists number drill set, the low quality manufacturing on imports often doesn't get the hole made all the way through the casting. you will see the divot in the bottom of the reservoir but it doesn't go all the way through. That will cause exactly what you describe the brake pressurizes and won't release. By the way this is a dangerous condition. As the brake drags it heats the fluid, with nowhere to go it causes the piston to push the pads harder, making more heat..... you can see where this heads. It happens with old dirty MCs too. that port being plugged is very common.
Had it happen on an old Honda 1100F test ride the rear rotor was glowing before I figured out why I didn't have much power....

"collapsed" or shedding hose can be the problem too. Always good to replace old hoses. But they tend to make bleeding hard and are not usually so restrictive. Has the caliper been rebuilt? That should (must) be done too, a sticky caliper is the MOST common cause of brake drag. Bill made some great threads on doing it, a rather easy job. Check up in the TECH button found atop every page.