Topic: 500 - Front brake issue, next step? [Update: fixed]

[Chachi]

I've been reading and trying to troubleshoot my front brake and I am in need of some guidance.

-Added SS lines a few months back
-Developed a slight 'leak' at the bleeder screw
-Replaced original bleeder valve screw with new Honda part
-'Leak' seemed to disappear with new bleeder valve screw
-Then started noticing some front brake drag
-Confirmed with bike lifted/front wheel off ground
-Adjusting screw has no effect on drag
-Piston appears to be sticking, not disengaging fully

Next step - remove caliper? I was debating doing that with the bleeder valve screw leak anyway. I can get a repro caliper body. If the drag can not be resolved with the adjuster screw, is it definitely the piston sticking? And if so, removing caliper is the next thing to try, correct?

Note: It's a new repro MC, so the small hole has no blockage, etc.

[phil71]

if you can crack the bleeder and the drag remains, you're going to have to clean up that caliper. Usually you can get a piston and seal kit pretty reasonably. If you crack the bleeder and it's still sticking, something up top has gone wrong. I never heard of a reproduction MC for a cb 500. Do you mean rebuilt?

[speedwolf]

I've had this issue before. A few things to try:

-There should be a slight clearance between the static pad and the rotor. I can't remember the exact spec, but I'll try to find it. You'll most likely have to disassemble caliper to release the pressure currently creating the sticking.

-Remove piston and clean out the chamber. Remove piston seal and clean out any crud inside that groove. I was surprised at how much I found.

-I also found lubricating the seal, outside edge of piston, and even a little on the outer edge of the brake pad puck (metal part) will help with any sticking.

[speedwolf]

From what I just searched, I believe the gap should be .006"

[RAFster122s]

There are some Chinese made master cylinders and there are reproduction MCs by firms like DSS and other reputable shops. Not all the Chinese or far east master cylinders are junk, just expensive to gamble with them to find the good ones.

[Bootlegger56]

+++++1^
"-Remove piston and clean out the chamber. Remove piston seal and clean out any crud inside that groove. I was surprised at how much I found."

If my forum ejecation serves me correct....the seal is what provides the retraction of the piston.  If the piston and caliper bore are clean and the piston slides in and out freely then I would address the seal groove with 0000 steel wool and make it shine especially the inside and outside corners.  Like above...I found a lot of crud in the bottom of the seal groove.

[Chachi]

The MC is like this one:
http://www.davidsilverspares.com/CB500K1-FOUR-1972/part_123893/

It sounds like I will need to check out my caliper, which is fine - I just wanted to make sure that is the next thing to try. Specifically - I wanted to confirm that the drag could not be caused by something else like insufficient bleeding. I bought a speedbleeder for all future bleeds, so if bleeding has anything to do with this symptom, I can easily give that a try first.

[bryanj]

Remove, clean and grease the pivot pin on the swinging bracket as well plus don't forget to check the tiny hole in the master cylinder-----do a search its been mentioned lots of times!!!

[LesterPiglet]

Note: It's a new repro MC, so the small hole has no blockage, etc.

Note there are two holes in the MC, one is tiny.

[Chachi]

I wanted to add some pics and ask a few more questions.

-The pics were after the first round of cleaning - Brakleen with 0000 steel wool.

-I can get the caliper a little cleaner, but not much more with what I have. I've also been gently scraping out the seal groove. The mechanic at my local Honda shop showed me a dremel attachment he uses for cleaning out the groove (while working on his flawless '70 750). I'm trying to do this right, but also somewhat limited on tools.

-The piston looks like what you see all the way around.

-From here should I keep cleaning as best I can and reassemble? I have a new seal and some lubricant for the seal.

-I do not have any high vacuum grease for the backs of the pads, nor does the pad on the piston side have the nylon ring.

-Also, the piston side pad is not worn evenly, should it be? I can add a pic if it would help. I would have picked up new pads today at my Honda shop, but they did not have them in stock.

[Chachi]

Pad pics...

[Chachi]

Right now I am leaning toward getting a repro caliper body and piston unless others here think mine are OK to use. I am definitely going to get new pads.

For the lube...

I see the advised choice for behind the pads is Dow Corning High Vacuum Grease, but what about for the caliper seal? I can not find an advised brand name. What about Permatex Ultra Disc Caliper Brake Lube (the back of the packaging specifically lists seals)? NAPA stocks that Permatex.

Also, my assembly does not have the nylon ring behind the pad - can I source another one or is it OK without?

[wowbagger]

I took my caliper and piston to a bike shop and had them hone the body and smooth out the piston. Cost me $25 in total. I used the dow corning on the piston ring and this stuff on the brake pad:
http://www.amazon.com/gp/product/B005JVNNDG/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1

The nylon ring behind the pad is not necessary. If one comes with the new pads then use it. If not, then you're fine to go without.

[reddyvv]

The caliper looks like it's usable if it has a good cleaning, as long as there are no scratches in it. The piston is pitted and needs to be replaced. If you don't want to deal with the hassle you may just want to buy a new caliper as well, the repros aren't that expensive. You don't put any lube on the seals anywhere, other than some brake fluid to lubricate when installing. Just very lightly coat the back and the sides of the pads with a suitable anti-seize.

And you absolutely do need to have the nylon ring behind the pad as it helps center the pad on the piston. That's why your pad is worn unevenly. It also serves to cut down on brake squeal and insulate the piston from pad heat.

[wowbagger]

Read this FAQ on how to rebuild the caliper:
http://forums.sohc4.net/index.php?topic=259.msg207521#msg207521

[Chachi]

wowbagger - I've read the FAQ, which has promoted some of my detailed questions. Also, you said you used Dow Corning on the seal and Wildwood on the pads? Not the other way around?

reddyvv - Were the nylon rings initially supplied with pads as they are not in the parts fiche. If I do need one, where can I get one?

[LesterPiglet]

Only type of grease I ever used was Copaslip around the metal of the pads and on the back. I use brake fluid on assembly.

[reddyvv]

reddyvv - Were the nylon rings initially supplied with pads as they are not in the parts fiche. If I do need one, where can I get one?

If you buy OEM as a set they do but if buying aftermarket it would be prudent to ask first.

[Chachi]

I'm going back to my local Honda shop today to order pads, but when I asked yesterday they said they didn't come with the nylon ring. I will ask again today.

[Djfob]

Nylon ring is not supplied with ebc pads.  I'd replace that piston for sure, mine didn't look nearly as bad and replaced with phenolic piston. These don't need nylon rings.

[RAFster122s]

Caliper looks usable if you totally clean the groove for the seal. Dow on pad edges and back and brake assembly lube on the piston seal. Don't use the permatex stuff, junk for bikes... if you can't get the assembly lube from NAPA them just use plenty of brake fluid on the seal. Do not use silicone of any kind on seal, it will contaminate the fluid.

[Chachi]

Local Honda was not able to source OEM pads nor have I had any luck online. I guess I'm looking at EBC FA13 or something else. DSS has some which may be EBCs, but I can't tell for sure (they're unlabeled aftermarket), but they do look to have the nylon washer.

[bryanj]

With new pads clean off all tha paint on the outer edge or they are too tight in the caliper. Have you checked the pivot pin yet?

[Chachi]

bryanj - pivot pin = the part that holds the caliper and moves with the adjuster screw/spring? The caliper is off and that moves freely by hand; fixed against adjuster screw setting.

I was debating re-using my caliper body and piston, but finally decided to order the DSS repros of both. Once those and the pads get here, I will get this thing back together. I also ordered some Wilwood assembly lube for the new seal and Dow high vacuum grease for the back of the pads. Hopefully it will all be in by the end of the week.

[bryanj]

The pivot pin is the steel pin that the caliper bracket swings on, has a big bolt at the bottom and a small alloy bracket at the top with 2 6mm bolts that also hold the fender, this comes off the pin and the pin should be a very free fit in the alloy swinging bracket