Author Topic: Is my brake caliper piston toast? (Read 5237 times)

csendker · « **on:** January 11, 2006, 06:31:34 PM »

Just got it out and cleaned up (used the grease gun, what a cleanup job...). Unfortunately, it looks pitted; is this toast or can it be revitalized somehow? If it's toast, where do you get replacements? I've looked briefly, but only found the rebuild kits.

csendker · « **Reply #1 on:** January 11, 2006, 07:01:21 PM »

...while the caliper itself seems to be cleaning up nicely. No pitting or other nastys in here to report. The seal popped out with no problem, still pliable (but not to be reused). There was brake fluid charged in it when I acquired the assemblt (I got everything from the handle/master cylinder on down).

Bob Wessner · « **Reply #2 on:** January 11, 2006, 07:10:28 PM »

Quote

Is my brake caliper piston toast?

I'm afraid so. Check out the parts FAQ for sources, they are available.

mrbreeze · « **Reply #3 on:** January 11, 2006, 07:30:15 PM »

I paid a pretty penny for one from the dealership but have seen them on ebay that are way cheaper.One guy had some that were special made out of a different metal that wouldn't corrode like the stock gem.

csendker · « **Reply #4 on:** January 11, 2006, 07:38:51 PM »

I found one at Old Bike Barn, but is seems to be hollow, while mine is solid??? Maybe this is one thing I should pop the $$ for at the dealer, it's always nice to be able to stop.

csendker · « **Reply #5 on:** January 11, 2006, 07:54:46 PM »

That must be some expensive filling in the piston. The hollow one from OBB is $23.95. Service Honda has (presumably) the real deal for $63.60. Yeesh. I'll have to call tomorrow to see what the local shop has to offer.

Jughead · « **Reply #6 on:** January 11, 2006, 08:03:35 PM »

Send me an Email with the Measurements and a Picture of the Pad Side I think I may have a GoodUsed one.

TwoTired · « **Reply #7 on:** January 12, 2006, 12:16:29 AM »

I believe your caliper piston is usable. Replace if you wish. But, I have used ones that were worse without incident and they functioned properly without leaks.
What are the drawbacks?
Stopping won't be a problem. However, if the pitting aligns with the seal, puck retraction will be slow and extra drag may result. Severe cases heat the disc rotor.

I'd try it. If it drags beyond your desires, then replace it. Lately, I've even been reusing the rubber seal if feels pliable and resilient and isn't deformed.

My opinion/experience.

oldbiker · « **Reply #8 on:** January 12, 2006, 01:11:40 AM »

There is a guy who regularly sells caliper pistons on eBay made from a phenolic material. I havn't used one but I've read sevaral complimentary reports. They are quite cheap too.

mutters · « **Reply #9 on:** January 12, 2006, 01:27:20 AM »

Is the 'solid' piston really filled in ??
My old k1 piston has a cap over the end, for no apparent reason,but as it has a twin brake conversion I can't guarrantee it's not off an earlier model.
Your piston may be the same

Raul CB750K1 · « **Reply #10 on:** January 12, 2006, 02:00:20 AM »

You can tray the phosphoric acid with the rust; it will eat up the rust and leave a smooth surface if the metal has not been eaten up; or maybe a very soft wire wool or sandpaper. I would also give it a try, but won't risk with the seal; it's only a couple of bucks original Honda part.

Raul

TwoTired · « **Reply #11 on:** January 12, 2006, 02:55:39 AM »

The original piston is chrome plated. Not certain what phosphoric acid will do to the chrome. But, removing the chrome or making it less slippery doesn't strike me as a good idea.

Cleaning the pits doesn't seem productive. And deepening them with acid is counter productive. I use brake assembly fluid to arrest the rust process, or at least delay the onset. I do try and keep the pit edges smoothed/ rounded with emery cloth.

If you don't feel qualified to assess the seal condition, then replace it. I allways used to replace it until I had the new one next to an old one and if they looked and felt the same, I began to question why replacement was needed. Though some of the old ones were clearly distorted. I've only reused a couple of them. But, they are still working fine.

Cheers,

Bob Wessner · « **Reply #12 on:** January 12, 2006, 03:07:44 AM »

Seems to me there just some things you don't take chances with, tires, chains/sprockets and brakes. There's a lot riding on them, pun intended.

csendker · « **Reply #13 on:** January 12, 2006, 04:51:27 AM »

I probably could reuse this one, but considering the whole reason I'm rebuilding this is because my existing brakes drag somewhat, I'd rather try to upgrade to a better piston to minimize the potential of slow/bad retraction. I was just surprised to see the replacement one pictured hollow when mine is capped/filled with something. And even more surprised with the price spread between aftermarket & Honda.

I looked for the ebay guy, but couldn't find anything. I'm going to mic my existing one, and if Jughead has a good used one, I'd rather upgrade. Or, I'll consider getting an aftermarket piston unless someone can convince me a hollow one is a bad thing. Mine definitely is capped, and seems to be filled (heavy). The picture of it sitting on my computer clearly shows the cap-thing. Who knows, this may be an aftermarket piston and it should have been hollow all along. What are they normally?

And I'm definitely going with a new seal. I agree with Bob on this one, and would rather not take chances until I'm much, much more familiar with the potential consequences. Epically on the brakes. Of course, that doesn't mean I'm throwing this one away.

Terry in Australia · « **Reply #14 on:** January 12, 2006, 04:59:33 AM »

Good point Bob. I'd replace it, there was a guy on Ebay selling stainless steel pistons that will not be affected by rust or knackered brake fluid like the OEM chrome plated steel items.

I've got some Brembo twin opposed piston calipers that I bought for my racer, and was surprised to see that they have alloy pistons, albeit anodised, with a special coating added to make them less likely to be damaged by the afore-mentioned nasties. A lot bloody cheaper than the Honda items too, at $25.00 US per PAIR!

Oh, by the way, your piston/s aren't solid, they have a cap with a slight "dome" which allows the pad to "pivot", so as to maintain flush contact with the disc and wear evenly. Cheers, Terry.

Bob Wessner · « **Reply #15 on:** January 12, 2006, 05:01:07 AM »

csendker,

I'm assuming we're talking about a 750K1? If so, I checked my parts list that covers the 750, 750K1 and 750K2. All use the same piston (part#), hollow with a metal cap. My K0 piston is like this.

Maybe that additional mass in your filled piston is adversely affecting how it withdraws?? Don't know, just a thought.

csendker · « **Reply #16 on:** January 12, 2006, 06:47:36 AM »

550 K1

Bob Wessner · « **Reply #17 on:** January 12, 2006, 07:21:39 AM »

Oops, sorry, can't speak to that then. $:-\$

csendker · « **Reply #18 on:** January 12, 2006, 08:18:24 AM »

Mind you, this is out of the spare caliper I bought, not my bike. So if the 'additional mass' does adversely affect piston retraction, it was for someone else. Anyone with a 550 out there know if they're like the one I have (capped, presumably filled)? Or can get (hollow & open)?

bryanj · « **Reply #19 on:** January 12, 2006, 08:48:45 AM »

500(twin and four)/550/400/250 (never seen in US)/360 All used the same piston WWW.davidsilverspares.co.uk did have stock at, i think £25 + shipping. You can use one of the Wing ones, its fractionally shorter and has a groove at the end for the dust seal that you dont use--works perfect in mine I did have some kits which cost me £17.50 and included the seal if you want me to look PM me

csendker · « **Reply #20 on:** January 12, 2006, 09:14:30 AM »

I found the SS piston ebay guy:

http://cgi.ebay.com/ebaymotors/Honda-CB750-K-CB-750-450-CB450-new-brake-caliper-piston_W0QQitemZ4603928161QQcategoryZ35592QQrdZ1QQcmdZViewItem

Looks like 750 only, no 550's. I'm going to measure mine tonight (after getting some calipers on the way home) and weigh my options.

DSS does have them:
CB550K3 : Brake caliper piston .... £22.00
CB550K3 : Brake caliper piston oil seal .... £1.95

bryanj · « **Reply #21 on:** January 12, 2006, 09:22:12 AM »

As I remember it the only difference 750 to 550 piston is length so why not ask that ebay seller if he will do you a shorter one

TwoTired · « **Reply #22 on:** January 12, 2006, 10:17:26 AM »

The pictures of your caliper pistons look just like the one in my stock Cb550s.

csendker · « **Reply #23 on:** January 12, 2006, 10:56:17 AM »

38 mm diameter & 34 mm tall. No dome on the 'capped' end.

Terry in Australia · « **Reply #24 on:** January 12, 2006, 01:57:27 PM »

50 bucks? Geez, time to fire up the lathe!

csendker · « **Reply #25 on:** January 12, 2006, 04:44:04 PM »

So if the stock piston has this cap-thing on the end, is there any issue using an aftermarket piston that's open?

dusterdude · « **Reply #26 on:** January 12, 2006, 04:49:06 PM »

no,doesnt matter

Terry in Australia · « **Reply #27 on:** January 12, 2006, 05:03:20 PM »

Quote from: csendker on January 12, 2006, 04:44:04 PM

So if the stock piston has this cap-thing on the end, is there any issue using an aftermarket piston that's open?

Put the cap on it, if it'll fit mate. cheers, Terry.

csendker · « **Reply #28 on:** January 12, 2006, 05:51:09 PM »

The cap-thing seems to be a permanent feature. I have no idea if/how it would come out. And I'm not sure it is necessary, or it would be included with the replacement.

Barrett99 · « **Reply #29 on:** January 12, 2006, 07:03:31 PM »

The guy on ebay who sells the phenolic piston has a good product, he cuts them down from a Mercury Lincoln part.
I installed mine with new pads, stainless lines and a master cylinder kit. Use Dot 5 fluid also. No rubber problems, no noise,
no gunking fluid. Check ebay listings for the various cb models, he usually has an auction going on.

mrbreeze · « **Reply #30 on:** January 12, 2006, 07:41:46 PM »

OK!!!!!----Now that you all have the piston prob. worked out ....lets go back to the problem of it not releasing. Go back to the good ole archives and read!!!(READ DEEP!!!) Remember the the little tiny compensation hole in the master cylinder reservoir? ""MAKE SURE!!!"" that this is not plugged with 30 year old flem,#$%*,garbage!!!! Always go to the archives if you don't find the answer on the recent posts!!!! (Hope this helps!!!)

csendker · « **Reply #31 on:** January 12, 2006, 08:02:14 PM »

Archives? I just did a search for: "compensation hole in the master cylinder" and came up with nothing. I read the brake FAQ also. What am I missing?

csendker · « **Reply #32 on:** January 12, 2006, 08:11:39 PM »

I found a link to "Greenspun Archives", but it's broke (Quote: "Sorry, SMF was unable to connect to the database. This may be caused by the server being busy. Please try again later." endquote). Are these the archives of which you spoke? I also checked my Clymer manual, and (big shock here) nothing.

mrbreeze · « **Reply #33 on:** January 12, 2006, 09:22:29 PM »

Just look into your reservoir.You will see a very small hole in the bottom. I was told to use a small guitar string and poke through that hole.Worked for me.Just be careful not to spill the brake fluid on anything(Will definetly eat paint!)Try it and good luck.

csendker · « **Reply #34 on:** September 26, 2006, 08:49:27 AM »

Here's the results to date:

Those pictures were actually of a spare, but I have no reason to believe my current piston is any better. So I bought one of the phenolic pistons but it's still sitting on my workbench with most of the rest of the front brake rebuild parts. It's still sitting because since this original post, I replaced my handlebars from the low-rise bars that came with it to a set of OEM standard bars. In the process, I found the PO replaced the top brake line with a shorty SS braided line to accommodate the lower bars and it no longer fit. Fortunately, I had a spare old, but still serviceable lines off some of the brake stuff that I had been acquiring. In the end, I dumped the fluid, replaced the lines (albeit temporarily with old), refilled with new fluid and bled them out. Shazam! Now everything's been working quite nicely and the brakes are much, much firmer with no perceptible dragging. I'm still going to rebuild the whole mess, but the focus has been on riding, not wrenching. Now with the onset of crappy Buffalo winter weather, that will change.

Moral of the story: When you buy a new ride, dump the old brake fluid, replace and bleed. It's too important a system to be running around with old, unknown quality fluids coursing through your brake lines.

And when I finally get around to my brake job, I'll try to remember to post the results.

News:

Author Topic: Is my brake caliper piston toast? (Read 5237 times)

Jughead

Barrett99