Topic: Caliper piston. Time to replace it?

[zenocchio]

My piston is a bit pitted, I had sticky and squeaking brakes this summer even if I rebuilt them. I did not change the brake lines because I was waiting to change my bars first. Now I have ss lines and new clubmans so I'm ready for a rebuild. Can I still reuse the piston or should I change it? It is slightly pitted but I don't have any experience so I am asking this forum.
New is about 90$ at the dealer here in Vancouver so before getting a new one I just want to make sure that this one is not good:

[Hastenbrucke]

750 K3 just did mine and my piston looks remarkably similar. I will replace it as well as the o' ring. Reminded to use some rubber grease on the o'ring and advised to make the whole thing spotless especially the groove the o'ring fits into. Pretty important part of the overall picture.....you don't want to get thrown off or not stop!!!!!

[Jerry Rxman Griffin aka MuthaF'er]

IMO - All depends on where those pits are in relation to the seal as the piston moves in and out. If it doesn't leak brake fluid with a good seal then you should be good to go.

[Clyde]

I would replace it as those small pits will allow brake fluid past them. If you are replacing the pads that usually will make the leak worse as the corroded part of the piston is now down closer to the seal..
If you are looking for a new piston I have found these to be excellent. They are stainless steel.

http://www.ebay.com.au/itm/Honda-CB-750K-750F-750A-75-78-Hondamatic-brake-caliper-piston-stainless-steel-/231095068029?pt=Motorcycles_Parts_Accessories&hash=item35ce56e57d&_uhb=1

Clyde

[brewsky]

Got mine from ebay seller "twowheelsfrank".
Shipping time was quick and OEM Honda seal included...
http://www.ebay.com/itm/Honda-CB-750-Four-K0-K6-Edelstahl-Bremskolben-Dichtring-brake-piston-seal-/360509498255?pt=DE_Motorradteile&hash=item53f00a638f#ht_0wt_0

[Henning]

That may well work; mine is similarly pitted and surprisingly it doesn't leak, even though I have been through the wear limit/new pads cycle. I don't see it as a safety issue as long as you keep an eye on it to check for leaks. Of course, it's a PITA to have to change out later when you just assembled everything, so you might want to consider that as well. I would go for the original chrome piston rather than SS, as SS and aluminium don't work well together - lots of posts about that.

[Chachi]

What does the inside of the caliper body and seal groove look like? If those are pitted as well, might as well get a reproduction caliper body and piston and new seal. I got mine from David Silver Spares. If you have it apart, better to do it once now vs. doing it again in a few weeks or months b/c you reassembled with pitted parts. If the caliper body and groove look OK, then DSS has some reproduction pistons and for less than OEM. There's a bunch of other repro pistons on eBay too.

[brewsky]

That may well work; mine is similarly pitted and surprisingly it doesn't leak, even though I have been through the wear limit/new pads cycle. I don't see it as a safety issue as long as you keep an eye on it to check for leaks. Of course, it's a PITA to have to change out later when you just assembled everything, so you might want to consider that as well. I would go for the original chrome piston rather than SS, as SS and aluminium don't work well together - lots of posts about that.

It would be interesting to see any actual results of the stainless pistons used for any period of time.

We have already seen what the chrome plating does.

Chrome and stainless are pretty close on the galvanic chart, and the common 304 stainless contains chrome for corrosion resistance, so there should not be that much difference between them?

The bigger arguement would be stainless vs zinc plated fasteners in aluminum alloy, no question there.

The phenolic version pistons should eliminate the arguement all together, if they are still available.

[zenocchio]

Thank you everyone for the reply, just to clear things the bike is a cb500, and i never noticed any leak from the caliper.

the pitting is unfortunately where the seal seats, i will look into a new one next year, keeping an eye on it in the meantime.

[/quote]

The phenolic version pistons should eliminate the arguement all together, if they are still available.
[/quote]

where is this one available?

[brewsky]

I believe it is member "kevin400f"

[RodPlunger]

I am kinda going through the same thing right now.. I just bought a used caliper and piston from a local shop, and the tech guy there said that the piston I have (which looks very similar to yours) should be just fine. It moves well in the housing and seals well against the o-ring... I'm guessing you should be ok.

[flybox1]

please see this thread
http://forums.sohc4.net/index.php?topic=132085.0

[Duke McDukiedook]

Yeah, talk to Kevin if he still does the phenolic pistons, way better than doing stainless.