Old brake caliper piston seals???

Question

I have a CRF250R, and my brakes work very poorly. It is not easy to stop as it used to be. I am wondering if the caliper piston seals could be corroded because I did bleed the brakes, and refill it. But it could have been a bad job. I will try it again.

Pretty much my question is can corroded seals not only hold the pistions on the brake pad but make it not stop well? Maybe by binding it or something.

Let me know

Thanks!!

Answer 1

Motorcycle brakes are very hard to bleed and you might want to waited over night and try it again.  Sometime gravity will help great time to change the pad as well and making sure it is not soak with brake fluid.

Answer 2

If your bike uses type 3 fluid, it is hydroscopic,  (absorbs water) I would disassemble the calipers and check for corrosion and scoring on the pistons and in the piston bore.

If, you have mixed type 3 or 4 with type 5 You now have glue in the system and complete dis- assembly cleaning and rebuilding is needed. Type 5 is a silicone base and doesn't mix with any of the others. It turns the fluid into a viscous liquid which won't flow through the lines.

Answer 3

Bleeding the brakes is something you do after you refill, merely emptying the reservoir and hoses is not bleeding.

There will be a bleed nipple on the caliper that you use, you can make a bleed kit with a tube and a jar but it is simpler to buy a cheap kit. The aim is to get all the air out of the system (air compresses and don't apply the brakes correctly, if at all). While you a doing this you might as well remove the caliper and examine it, seals do go and are relatively simple to replace – since you have to empty the system to do this do it before you refill – but they don't hold the pistons in they are there to stop the brake fluid getting out.

In short I suspect your problem is that there is air in the system and that it can be bled out. Be careful with brake fluid it will destroy paint if it gets on your bodywork, it also attracts water do not be tempted to use an old opened bottle of fluid even through the tightest cap it will have leached moisture.

http://www.totalmotorcycle.com/maintenan...