Topic: Front Brake Overall Problems

[kansassteve]

I have a '74 CB550. I want to overall the front brake as the bike has not ran in years.
I have a few questions.

How do I remove the brake pad next to the piston? it just will NOT move!!

What is the best way to clean out the system? do I need to strip every thing down?

Lastly, where is the best place to buy a rebuild kit for the master cylinder?

Thank you in advance, Stephen

[MikeDeB]

Sometimes you have to remove the pad and piston at the same time.  It won't come out because there is a lot of crud built up between the edges of the pad and the caliper.  You can remove the piston/pad by using the bikes hydraulic system.  Just slowly pump the brake lever and keep an eye on the pad.  It will move out far enough so that you can remove it by hand.  Once it's off, finish removing the piston by pumping the brake lever slowly.

I have found that denatured alcohol is an excellent solvent for cleaning brake parts.  Follow that with a good washing with dish soap and water.  Then blow dry with compressed air.

I bought my master cylinder rebuild kits from Partsnmoreonline.com.  You will also want to get a caliper piston seal to replace the old one.  You may also need a new piston depending on it's condition.

You may find a buildup of corrosion in the seal recess of the caliper and the end of the master cylinder where the circlip goes.  I've found that a small wire brush attached to a dremel tool works wonders for cleaning this off.  Just be sure to wash the parts after the wire brush and blow dry.

[kansassteve]

Hi, thanks mike for your info. I have tried using the brake lever but the pad and piston just will not move, any ideas??
Thank again, Stephen

[Bob Wessner]

You can try disconnecting the brake line, make sure the bleed screw is tight and apply a few threads of a small grease gun to the brake line hole and pump. It should push the piston and pad out.

[kansassteve]

Hi, do I actually pump greese into the brake unit? I'm a bit unsure. Thanks for the help, Stephen

[Bob Wessner]

Yes, it means some clean-up in the caliper, but you're going to have to get in there anyway. Remember, you want to remove the grease fitting thingy from the end of the grease gun and just barely grab a couple of the threads to the brake line hole because they likely are not a thread match. Some folks have used compressed air to do this, but I had no source for it and this way avoids the sometimes explosive affects once the piston releases.

[kansassteve]

Thanks for the help, I will give it a try, Stephen

[Flood]

Compressed air worked for me everytime. Just be sure to hold a rag on the caliper, lest it rockets in you face!

Remi

[MikeDeB]

Hi, thanks mike for your info. I have tried using the brake lever but the pad and piston just will not move, any ideas??
Thank again, Stephen

Hi Stephen,  Was there fluid in the system when you tried forcing the piston out with the lever?  And if so do you know if there was any air in the system?  If you had a solid lever and it still wouldn't push the piston out then the piston or pad or both are really stuck and compressed air won't budge them I'll bet.  I've had one come out very easily with compressed air but the most recent one I had to pump out using the brake system after 125 psi of compressed air didn't do a thing.  You could try heating the area around the pad with a propane torch to see if that will at least dislodge the pad.  Do so very gently if you try this.  Another option is to hose down the seam between the pad and the caliper with spray brake parts cleaner and then try pumping the piston out again with the lever.

When I had gotten to the point of trying to remove the pad and piston on my most recent rebuild I had already removed the caliper and master cylinder from the bike.  What I did was to mount a spare handlebar in a bench vise and mount the master cylinder to it.  I then reattached the lower brake line directly to the master cylinder with the other end attached to the caliper (eliminating the upper line and junction block/brake switch).  I let the caliper hang and with the bleeder screw closed, filled the resevior up with brake fluid.  After stroking the lever for a few minutes it developed resistance and the pad/piston began to emerge from the caliper.  Didn't even have to bleed the system.  Also, prior to stroking the lever I did spray down the edges of the pad with brake parts cleaner.  Another thing to consider if the piston is really hung up (and might be from gummy old brake fluid) is to use denatured alcohol instead of brake fluid.  Just be very careful using it.  It is an excellent solvent when cleaning brake parts.

You can always try the grease gun method but once you do you can't return to any other method using brake fluid (the two won't mix).

Hope this helps and good luck.  Let us know how you make out and/or if you figure out another way of getting the parts free.