'81 Interstate rear brakes

[D-50Dave]

On the way home from work the light turned yellow at that awkward moment, and I through on the binders hard. The back locked up and wouldn't release. Dragged it home without it catching on fire. :beg: I'm looking for some advise about the master. I'm going to rebuild the caliper, should I rebuild the master as well? It's been dragging slightly for a month or so and I was going to do this in the off season, but circumstances.... I could use all the input I can get. Thanx, Dave
P.S. Is this what I'm looking for?
https://www.ebay.com/itm/Honda-New-K-L- ... 6405!US!-1

 

[Omega Man]

Slightly off topic but what could cause this to happen? The piston pushes out far enough to to slip out of it's orifice making it impossible to slide back in?

~O~

 

[pidjones]

Usually the return hole in the MC is plugged. When you remove the MC from the bike, you will find a bolt in the side of it with a common aluminum sealing washer. After removing the bolt (and probably rinsing the area with brake cleaner) you should see an indention in the body inside that has a tiny hole in the bottom of it. Take a high G string from a 12 string set and poke through to open it up then spray through it with brake cleaner. Rebuild the MC, put a new aluminum washer under the bolt and tighten it. Although crud and corruption can cause a caliper to stick, usually not both pistons at once, and they can't come out of the cylinder unless removed from the disk and pads removed. The MC return hole is the most common culprit by far.

 

[D-50Dave]

So then I would need this? I'm thinking of going with both.
https://www.ebay.com/itm/1980-1981-HOND ... 6405!US!-1

 

[pidjones]

Honestly, I'd start with some sealing washers, brake cleaner, and fresh fluid. Don't remove the circlip - leave that assembled. You have to remove the line from the MC to get the MC out. Remove the diamond-shaped flange (4 on the diagram) that connects the reservour so you can access the tiny return hole, clean it all up and flush with clean fluid, put it back together. If the system has been well maintained (fluid flushed every couple years, pistons cleaned off before pushing back in when mounting new pads) that should do it. Otherwise, Yes you need both MC kit and caliper kit. I always cross-check part numbers from a Honda parts list like the ones at Southern Powersports.
https://parts.southernhonda.com/a/Honda ... A14ZA.html

 

[mcgovern61]

It is an '81 so only one piston. The '81 master cylinder and '81 caliper are more prone to this condition (getting stuck). Rebuilding the master first and all new fluid is the best way to start.

You can pull the caliper off, disconnect the brake line and see if you can push the piston in easily. If not, rebuild the caliper. The piston should be able to move without too much resistance.

 

[joedrum]

Well right now I’m into the same crap on single piston brakes and the pistons moving back and forth is the only thing doing great ...bleeders stuck on both sides and trying to bleed through master only ...sheesh what a nightmare ...I couldn’t be any more frustrated ...good luck :builder:

 

[Dusterdude]

Take a good look at the hose too

Sent from my LG-US601 using Tapatalk

 

[AApple]

I had an issue with the rear piston sticking on my '81, and it kept wearing the pads out fast. I finally bit the bullet and rebuilt the caliper, and solved that problem. I eventually rebuilt the master also, but I did that because I was just un-able to ever get a good, solid pedal on the rear....and still haven't. It will stop just fine, tho.

 

[saganaga]

My philosophy is that for the cost of the kits, rebuilding both the caliper isn't that expensive, and isn't a hard job. I don't think the caliper is the problem, but if you have to break open the system and bleed everything anyways, why not spend the extra $20 for the caliper rebuild kit?

OTOH, if it ain't broke...

 

[D-50Dave]

saganaga » Yesterday, 11:32 pm[/url]":2d3w828o]
My philosophy is that for the cost of the kits, rebuilding both the caliper isn't that expensive, and isn't a hard job. I don't think the caliper is the problem, but if you have to break open the system and bleed everything anyways, why not spend the extra $20 for the caliper rebuild kit?

OTOH, if it ain't broke...

Oh, its broke. I'm pretty lousy at detail maintenance. I don't mess with brake fluid flush and fill on my cars and they seem just fine, so I've always just left my brakes be. I'm gonna do both and then I can go back to ignoring them. :whistling:

 

[WalterM817]

I’ve had more bad rear brake luck because of the pedal sticking from rusted pivot points with the pedal.
They’re usually a mess to get off the pedal mount. Cleaned up and regrease the pivot point
That may not be the problem for a lot of folks but both my brothers 82 as well as my own had it happen.
Just something else the old dears will pull on you...

 

[D-50Dave]

The pedal works smoothly. Next month will be the 30th anniversary of my purchase and its lived inside for the last 28 years. Appreciate the thought, though.

 

[Ansimp]

My 81 drops out the MC as the retaining clip is corroded. I now have it wired up with ss tie wire and no more collapsed MC creating a no rear brake situation. More than likely it is the MC return orifice. Easy way to figure it out is drop the pressure out of the brake calliper if it frees it is the MC orifice if not it is a stuck calliper piston.

 

[D-50Dave]

Well, I took the day off and started on the brakes after lunch. I started at the caliper and once I had it off, this is what I found.

I got that pried out, got the caliper apart, stuck it in the ultrasound for cleaning, and moved on to the master cylinder. It took awhile to liberate it, I think its never been touched since the assembly line. I think I have the wrong rebuild kit as the push rod is way too short.

I've contact the vendor and we'll see where we go. I have a number of questions.
1) What do I use to lubricate the sliders that the caliper mounts to?
2) How thick should the rear disk be? Mine seems to measure about 6.2mm
Well, what a difference between when I started this post and now. I had bought the MC kit from BrakeCrafters on Ebay. Before starting this post I "contact(ed) seller". On a whim I gave them my cell#. 5 minutes later, my phone rings and its the pleasant British accent of Mark from BC. In the end it seems a previous owner, when adding the floor boards, changed the push rod to get the pedal to a more appropriate position. They given me a kit # that should have what I need. I'll keep you posted.
I have also buggered up the pad retaining clips.

Anyone know where I could find 2. they seem NLA.
https://www.cmsnl.com/products/retainer ... YlROShKjcs

 

[mcgovern61]

That rotor is not looking too good. It is marked in the center what the limit is.

 

[D-50Dave]

Anyone got a good rotor for sale? :beg:
...and those retaining clips.

 

[D-50Dave]

I found a post that said an '80 rear rotor was 6.9-7.1mm with a service limit of 4.0.
https://www.goldwingfacts.com/forums/2- ... width.html
So at 6.2mm, I'm OK?

 

[D-50Dave]

The clips are killing me. Part # 43112-410-006. NLA, and I can't find any used on Ebay. Any ideas? I may have to resort to straightening them out and hope the gouged out bits don't effect performance. Also, how should I lube the sliders the caliper rides on? Thanx, Dave

 

[mcgovern61]

6.2 mm is good if the rotor is not scored. From your pics, it looked like it was scored. I cleaned up my rear rotor on my '82 using an 80 grit sand paper on a grinder with the rear of the bike up on the centerstand and the bike is first gear. As the wheel turned I was able to gently let the high speed sander (circular type) ride the exposed side of the rotor and remove the glazed surface.

These rotors are tough! I believe they are stainless steel and not easy to cut. The clips are hard to find. Sometimes easier to get with a used caliper. However, if you take your time and bend nice and slow, you should be able to reuse yours.