Topic: CB500 caliper/piston - is it good enough? UPDATED PICS

[dkruitz]

Just got the stuck piston out of the caliper body - never had one of these apart before.  There are a couple of pinholes of corrosion on the piston, but I think I can smooth them down with 2000-grit wet/dry, same for the bore.  For certain none of the pinholes are big enough to cover the spread of the seal.  I also removed seal and cleaned the aluminum corrosion from the groove.  Rubber seal is flexible and seems decent - should I reuse it, or are these always replaced?  Can post pics if needed.

[bozo4onion]

I just got a seal. Cheap (<$10) and Honda still makes them. Change that thing.

[bryanj]

Change the seal, post a pic of the piston

[hymodyne]

I cleaned up an original piston in my first rebuild of the 500K1 in my avatar. 250 miles into a 350 ride with a friend through MA and VT, I noticed a lot of heat coming up from the rotor and that my  mileage had fallen off really badly. I discovered when I got home that my "fixed-up" piston ( I had sanded and polished out the pitted parts) had basically gotten stuck each time that i braked. IMHO, I'd drop the cash for the new piston, or the phenolic ones that are advertized on ebay. good brakes are worth the money...

hym

[754]

hym..were you using the adjuster bolt?? i take them out

[SteveD CB500F]

You mean you run the front brake without the adjuster bolt fitted?

Fully floating?

[754]

Always..

[hymodyne]

my bolt was in place. I thought it was necessary to get the proper clearance of the puck to the disc, per the shop manual...somebody talk to me as to whether I need them or not; I'm going to a set of 550 forks and dual discs in January, right after I get married...

hym

[Bob Wessner]

I'm with Steve. Honda seemed to think they served a purpose. Why do you run without it?

[dkruitz]

OK, I've got a photo, but it's not very good.  Between the resolution of my camera, and the focus distance, you can really get enough detail I don't think.

[754]

These were the first disc brakes used on a stock bike, not a lot of experiece behind them...

 Run the bolt if you will but, do a tire change on dual disc once, then tell me what you think..

[bryanj]

picture not good, need one of just piston where pits are

[dkruitz]

OK, I just took this with a much better camera - no flash used so the exposure is long and about as still as I can hold the camera.

The caliper body looks really discolored, but it's smooth.  Only thing I've done to any of this is clean it with brake cleaner, and scrape the seal grove out carefully.

The photo is at http://www.elginoutboard.com/caliperbig.jpg  if you need to see the fullsized image, as I believe the board shrinks it down.

[dusterdude]

my opinion is,if the piston is smooth and there are no burrs from the pits,i would run it,it doesnt look that bad to me.

[Deltarider]

That piston is O.K.

[dkruitz]

Thanks guys, I'm going to "polish" it lightly with some 2000wet/dry to be sure nothing is protruding, and see about a new seal.

[edbikerii]

That piston looks practically brand new compared to the one I've been running since the early '90s!

[bryanj]

OK piston is useable at present but will get worse and new ones can still be got at the moment but will get scarcer---your call

Still looks to be a bit of crud in the groove needs to be really clean, fit new seal lubed with brake fluid WEAR GLOVES; polish piston with finest wet and dry available (2,000 grade is good) using brake fluid as a lube and making sure there are NO raised edges on the pits Clean off ALL the crap and relube and assemble.

If you have a freind in a machine shop and can get some 1 1/2 inch (38mm)stainless for him to bore out you can make a piston