Topic: brake piston repair

[upperlake04]

Hello All - another question from under the shade tree-

  Front calipers from the 78 750F3 are disassembled and cleaned. One piston has pitting through the surface plating that appears to be adjacent to where the seal would normally be. No doubt this is the cause of brake fluid leakage. Has anyone attempted to repair damage like this? JB weld?  brazing?
   I expect the correct answer would be to replace the piston but this is a $100Cdn bike and I  have already spent enough on parts  for this untested bike over the past winter - is there a cheapy fix that will get me riding  to see what I have for a bike before I have too much into it?

[Bob Wessner]

Sorry, but I think you should replace it. Not sure how any composite repair material would hold up to brake fluid anyway. It's a pretty important safety issue... just my $0.02.

[KB02]

yeah, I'll back you on that. Brakes are too important to "Hope" something works on.

If you've got it apart anyway, clean it up and replace the seal and see if it still leaks. There's a good chance that the leak is caused
 by just dirt or a bad seal. If cleaning it out and replacing the seal stops the leak, you should be all set. If it still leaks, replace it.

[ofreen]

I have heard of guys successfully using JB Weld to fill in pitting on brake caliper pistons.  I haven't needed to try it myself, though.

[upperlake04]

thanks guys - ofreen,  I think I'll try the JB - put on the least amount possible and then before it is real hard fine grit wet sand carefully with the sandpaper wrapped around a small flexible rubber pad
  KB02 - of course you're right - I'll try it with all the crusty crud removed and the surfaces polished and with a new seal, might be tight. if not I"ll  get the wallet out   again
  Bob - nice to see you back to your gentle responsible self( after that brutal drubbing you gave the member from Aus - still don't think he's back yet - what were you and Mike on?)  The safety concern is valid, but remember I have an F3 - we have two (2) front brakes

[rucorey]

I know how part$ seem to add up, but there are nice stainless pistons avail on eSplay for like $50 US. I have some pitting on mine and I've sanded them down, but I'm not overly confident they will seal tight.

http://cgi.ebay.com/ebaymotors/Honda-CB750-K-CB-750-450-CB450-new-brake-caliper-piston_W0QQcmdZViewItemQQcategoryZ35592QQitemZ4636292114QQrdZ1QQsspagenameZWDVW

[anparkinson]

I had a badly pitted piston on my CB550. I had a local machine shop make me a new stainless steel one using the old one a as pattern. Cost me 10 Pounds.