Front Brake Rebuild

If it's broken or just needs tweaked

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Solomoriah
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Front Brake Rebuild

Postby Solomoriah » Thu Mar 02, 2017 10:23 pm

My 1980 CB650 is suffering from some dragging, not serious but noticeable. I hate to take it all apart and then be without my ride, especially at the beginning of the season, so I've worked out a plan.

I'm going to start by buying another front caliper, on Ebay of course. Or is it eBay? Whatever. I'll tear it down to its component parts, clean and inspect the metal bits, replace the rubber parts and any part that is too worn to use, then put it all together with some new pads and swap it for the one on the bike. That one may get sold... I even considered refurbing it too, and selling it that way (hopefully at a profit).

I've done tasks of similar difficulty before (at least, based on the research I've done) but I've not actually done a brake rebuild, so I'm asking for advice here. Specifically:

-- What kind of brake fluid should I use? I know technology has moved on since 1980, so if there is something better for this application than what the manual recommends, I'd like to hear it.

-- Are there any interesting substitutions here? That is, are there other calipers that will bolt on that might work better? The dual piston units from the later Nighthawks don't look like a match, but it's hard to tell looking at pictures.

-- Would a braided steel brake line be appropriate for this bike, and if so, can anyone recommend a manufacturer or reseller I should try?

-- Finally, any other advice on this project would be welcome.

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Folsoml
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Re: Front Brake Rebuild

Postby Folsoml » Fri Mar 03, 2017 8:29 am

Your dragging brake problem is most likely not caused by the caliper, but instead by the master cylinder. There is a small hole in the master cylinder that allows the brake fluid to return to the reservoir when you release the brake lever. This hole often gets plugged. As a result, when you squeeze the brake lever to stop, the caliper will not fully release because the fluid cannot return to the cylinder. To clean it out, remove the master cylinder oil cup to get access to the holes. I usually use a piece of high E guitar string to clear the hole out. That string will just fit through the hole. You may as well clean the rest of the master cylinder while you have it off.

Image
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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Fri Mar 03, 2017 9:55 am

And this is why I ask for help.

:D

Still, a question... If I'm going to have to empty the master cylinder anyway, should I completely replace the brake fluid? It's 37 years old, after all. If so, what do you recommend?

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Folsoml
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Re: Front Brake Rebuild

Postby Folsoml » Fri Mar 03, 2017 1:30 pm

I use regular DOT 3. I would definitely replace it.
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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Sat Mar 04, 2017 1:38 am

I'm going to be taking it apart anyway, so I suppose I should get a rebuild kit, right? How do you feel about the K&L kit, 32-1464? They claim it's all OEM parts required to rebuild the master cylinder, and it does look complete (comparing to the fiche, of course).

For the record, I got the bike with just over 6000 miles on it; it has just over 8000 now.

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Folsoml
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Re: Front Brake Rebuild

Postby Folsoml » Sat Mar 04, 2017 6:43 am

K&L makes good kits. I've used them many times.
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tario
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Re: Front Brake Rebuild

Postby tario » Fri Mar 10, 2017 2:23 pm

I've always been tempted to replace the levers with $50 amazon sets rather than doing a rebuild for the same price or more. I do imagine honda put out a better product than strangers from china on the internet. As long as the bore of the piston is the same and it's for 7/8 handlebars it should work the same... give or take quality control. They also have $20 braided lines on amazon.

Some people might argue that if you are going to spend money to do anything right... the brakes are the best investment. You know, safety...

I needed a vacuum pump to get fluid through the system. You can get a cheap one for $25 or something. I made the mistake of buying a fancy set for double that.
1979 cb650
1980 cb650

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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Mon Mar 20, 2017 11:21 am

So, an update. This morning I tried to do the rebuild. I had some difficulty getting the brake fluid out of the system, but eventually succeeded; next, I pulled the lever and mirror, unhooked the wires, and removed the unit from the bike.

According to the service manual, removal of the piston assembly is next. I pulled the nasty old boot off, and discovered the circlip was covered in rust, so much so that I could only see one of the two little holes. I used a screwdriver to scrape it off enough to remove, and then discovered that my circlip pliers aren't long enough (short about 5mm, gah).

I decided to go ahead and remove the reservoir, which was a bear to do; underneath was nasty crud, not as much as I expected but definitely a problem. I removed as much as I could, and having no way to continue, decided to reassemble the system.

The master cylinder does not work at all now, unfortunately. I obviously knocked some of that crud into the holes that permit fluid to enter and exit. Cleaning them would be simple enough, if I could get the piston out.

SO at this point, it appears I need to order a better pair of circlip pliers. I'm open to suggestions here. And how is the best way to remove the remaining rust, once I get the circlip, piston, etc. out?

I also need to replace the O-ring at the bottom of the reservoir, but that shouldn't be hard to find. I removed the reservoir by means of careful prying with a broad, flat-bladed tool, and reassembled it with a vice and some wood blocks to protect the unit from the vise jaws; having done it once, I'm confident I can do it again. (The O-ring is definitely not serviceable, as it leaked around the reservoir base; I emptied the unit before taking the tarp off of the bike.)

Or should I just give up and buy a whole new master cylinder? There are some nice-looking aftermarket units.

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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Mon Mar 20, 2017 12:03 pm

This unit, for example, comes highly recommended: https://www.amazon.com/dp/B01CCJKK2O

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Folsoml
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Re: Front Brake Rebuild

Postby Folsoml » Mon Mar 20, 2017 4:25 pm

I have a soda blaster that I will usually use on the circlip area before I try to remove it. It really cleans up the rust and allows you to see a much better.

You say it's not working, what is the master cylinder doing now? Did you "prime the pump" after putting it back together? With fluid in the reservior, I will put my finger over the hole where the brake line connects and pump the lever. You may feel a little pressure on your finger. Pull the lever and lift your finger to release the pressure. Cover the hole again before releasing the lever. Repeat this until all the air is out. The fluid should now shoot out past your finger.
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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Mon Mar 20, 2017 6:46 pm

Folsoml wrote:I have a soda blaster that I will usually use on the circlip area before I try to remove it. It really cleans up the rust and allows you to see a much better.

Soda blaster... hmm. Not familiar with that one, but it sounds brilliant.

Folsoml wrote:You say it's not working, what is the master cylinder doing now? Did you "prime the pump" after putting it back together? With fluid in the reservior, I will put my finger over the hole where the brake line connects and pump the lever. You may feel a little pressure on your finger. Pull the lever and lift your finger to release the pressure. Cover the hole again before releasing the lever. Repeat this until all the air is out. The fluid should now shoot out past your finger.

Okay, so that's a procedure I've not found in print up until now. Might fix my problem. I'll have to wait, though, as the O-ring still needs to be replaced.

Thanks!

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Folsoml
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Re: Front Brake Rebuild

Postby Folsoml » Mon Mar 20, 2017 8:59 pm

Solomoriah wrote:Soda blaster... hmm. Not familiar with that one, but it sounds brilliant.



It's basically a siphon feed sand blaster gun, but instead of sand, I'm using baking soda. Cleans things up nicely, but it's less abrasive.
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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Mon Mar 20, 2017 11:01 pm

Folsoml wrote:It's basically a siphon feed sand blaster gun, but instead of sand, I'm using baking soda. Cleans things up nicely, but it's less abrasive.

Just looked them up... too much expense for me to justify buying one just for this purpose.

Another question (tired of me yet?): When reinstalling the reservoir, do you put the O-ring into the metal housing first, or on the reservoir? I did the former, as I thought the relatively sharp edge of the housing might damage the O-ring, but the tapered barb on the reservoir looked less threatening. The O-ring was too rough to seal properly, which did not surprise me, and so I'll be replacing it... just want to do it right.

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Folsoml
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Re: Front Brake Rebuild

Postby Folsoml » Tue Mar 21, 2017 8:18 pm

I use the soda blaster for a lot of stuff.

O-ring goes in the housing. Lube it with some brake fluid before seating this reservoir.
Have a problem with your CB650? Have a technical question? Click here!


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Solomoriah
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Re: Front Brake Rebuild

Postby Solomoriah » Tue Mar 21, 2017 10:14 pm

Folsoml wrote:I use the soda blaster for a lot of stuff.

O-ring goes in the housing. Lube it with some brake fluid before seating this reservoir.

Ah, good. That's how I did it, and how I will do it again when I have a healthy O-ring. Thank you sir.


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