[jfisher34]

Hi, I am new to the forum and need some help. I got an 85 TRX250 fourtrax that needs A LOT of love and I stumbled on something that I cannot figure out. I tore the quad down to the frame and started rebuilding. I am currently trying to get the front brakes to work. I drained the lines completely and am struggling with getting them to work while attempting to bleed them. Here are my symptoms..

I can build pressure in the line
Air bubbles continue to form even after 30 minutes of bleeding
Air will come out of the bleeder screw and also float up in the master cylinder
The cylinder at the shoes will never move a millimeter on either side
I can get several "squirts" of solid fluid and then air will appear again sometimes tiny bubbles and sometimes bigger
I have tapped the lines over and over to force any air to move out

I am hand bleeding the brakes
I know to squeeze the brake, open the screw, close the screw, let off the brake handle
I never let the fluid drain to low in the master cylinder

I noticed the boot on the master cylinder set is torn

Do I have a leak in the master cylinder?

thanks in advance for your help!

 

[misterclean59]

I don't know if the slave cylinder is leaking or not but I would disassemble both slave cylinders because they are so old. Sometimes you can re use parts sometimes not. I'd check availability before I tore it down so as to be very careful with "unavailable" parts. To bleed I think you are doing good to tap the lines. The only thing I'd suggest is to pull the front brake lever all the way to the bar and hold it there with a zip tie. Unbolt both cylinders one at a time so you can position it in such a way that the bubbles go up.

 

[retro]

Also adjust the brake shoes all of the way out tight (brakes nearly locked up) against the drums at each wheel cylinder while bleeding. Back them off where they belong after the bleeding is successful.

You can remove the round rubber check in the bottom of the Master cylinder reservoir while bleeding, which will help speed the process. Note how it was installed when you gently pry it out of there so you won't reinstall it upside down.

Also put a clamp, pliers or vise grips carefully on the rubber brake hose near the master cylinder while you pump the lever. This will act as a check valve allowing fluid (and air) to flow toward the bleeders but not allow those flows to reverse back into the Master.

If you are still seeing air in the system after doing all of these things you probably have a bad cup seal (or a pitted bore) in the Master and/or the wheel cylinders. Finding pitted bores in the Master & wheel cylinders is common on old brake systems.

Let us know what happens if you can and welcome to the forums!

 

[jfisher34]

Thanks for the quick help.

I forgot to put in my original post that neither slave cylinder was moving at all no matter how much air I had squeezed out. I kept thinking there must be a massive bubble stuck somewhere or I was sucking in as much air as I was removing. I was refusing to believe that both cylinders could have the same problem. And I was WRONG!

it took a vise and vise grips to remove one side of each piston and then a hammer and punch to push out the other. after cleaning all 4 with a brass brush and a LOT of steel wool work, I was able to slide them in and out freely.

Put it all back together, bleed the brakes again and SUCCESS!

Thanks again for the advice. I am sure I will be back with more questions.

Before and After pics attached of the pistons.

 

[misterclean59]

Great news!!!!

 

[retro]

Thanks for following up to let us know how you fixed it!