Brakes

If it's broken or just needs tweaked

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1980cb650
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Brakes

Postby 1980cb650 » Sun Mar 12, 2006 11:32 pm

All last year my brakes were a little soft, and the fluid was nasty looking, so I just flushed the fluid in it. When I took the cover off the reservoir I noticed a bunch of crap in there. I cleaned it out as much as I could, and now it won't build up any pressure. I let it gravity bleed for awhile, so I'm pretty sure there's no air in there. Are seal kits available for the master cylinder, or should I start looking for a new one?

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Vatch
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Postby Vatch » Mon Mar 13, 2006 10:20 am

They do sell replacement gaskets for the master cylinder. I had a leaking MC and replaced it for a bit of money. There did not seem to be anything wrong with the plastic housing or visually anything wrong with the gaskets, but the leaking stopped. In addition to the air bubbles that could be in the line, air could be getting to the brake fluid from the outside, which would render the brake fluid less effective. Try twisting the handlebars about to get the brake fluid level above the upper gasket level. If there is a leak you are getting air into the brake fluid and may need to replace it and the gaskets. Torquing the screws on the MC lid is not an effective solution (so I've learned).

As for the air bubbles, it took me a good week to get them all out.
'99 1500 Drifter

cajun
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Postby cajun » Mon Mar 13, 2006 12:05 pm

You can definatly loose presure if the mc is leaking anywhere. Mine was leaking on both brake and clutch. I just got a rebuild kit with the cups and the boot and was good to go. I need to replace the diaphram and the lid because its another problem itself. A leaking lid will cause issues here and there, atleast it has for me. I would loose pressure here and gain it back somewhere else. crazy, But I am by far a pro, but had to pretty much rebuild this bike all the way around the engine. You might want to rebuild the slave to. Mine wouldnt hold pressure because the last little seal in the slave was leaking my fluid into the oil. Of course all the seals where bad so it was gonna have to be done. I didnt figure it out until I just couldnt find any fluid leaking and thought about how the bike works and bam. You will figure it out soon.

cb650
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Postby cb650 » Mon Mar 13, 2006 2:05 pm

You didnt get any of the crap down in it did you? Might be worth a rebuild. Your calipers might need a tention too.



Terry

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1980cb650
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Postby 1980cb650 » Sun Mar 19, 2006 6:14 pm

Well I bought a master cylinder rebuild kit off ebay. I took the MC apart after fighting that stupid snap ring in it. When I pulled the piston out, a whole bunch of dirt like crap came out with it. Definately no fluid moving through this thing. I was amazed the brakes worked at all last fall. Now I'm going to clean the MC, rebuild it, flush the line and caliper to make sure those are cleaned out too.

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1980cb650
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Postby 1980cb650 » Mon Mar 27, 2006 4:29 pm

Ok, so I rebuilt the master cyclinder and still no pressure. I bleed and bleed, but no luck. I took the caliper off and found that I can't push the piston back in, I think it's siezed. Question is, would a siezed caliper cause no resistance on the handle? Looks like I may be in need of a caliper now if anyone has an extra.......

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Vatch
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Postby Vatch » Mon Mar 27, 2006 6:42 pm

After flushing and rebuilding the MC it took a bit of work to get all the air bubbles out before pressure returned. The handle should have some resistance from the spring on the plunger in the MC.
'99 1500 Drifter

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Volker_P
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Re: Brakes

Postby Volker_P » Tue Mar 28, 2006 1:10 am

A stuck caliper will not relaese pressure. Where should it go to? If no brake fluid is coming out during pumping, you still have air in your system. You could remove the master cylinder with the first part of the brake hose and try to bleed this part separately (use a screw with two copper or plastic washers to plug the free connection ring). This way you can check if your MC rebuild was successful. Another advantage is that you can turn that part in any direction to get rid off bubbles in any corner. May be helpful to remember which turn brought the effect for later mounting on the bike.
If you get pressure this way, try it again with the complete brake on the bike. If you manage to get it working, use the pressure to push out the caliper and clean it. If piston and hole surfaces as well as gaskets are a still allright, it may be used again.
I am sorry that all this means splashing around with brake fluid, but I think it is quite straightforward to get the answers you need.
If you still have bleeding problems, you could also bleed the whole brake before you mount it on the bike again. Sometimes this turns out to be the fastest option. :roll:
Good luck!

canuck1sailor
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Re: Brakes

Postby canuck1sailor » Tue Jun 04, 2013 10:29 am

Is there a gasket between the MC lid and the reservoir? (1980 CB 650 C with 4 bolt reservoir lid) The manual shows that there is a gasket fitted; however the reservoir kits don't indicate a gasket is included. Mine does not have a gasket, it now leaks after cleaning and flushing. It did not leak prior to cleaning and flushing and the brakes work well as they did before.

Any ideas?

I was concerned about the age/condition of the brake fluid having just replaced all brake cylinders and master cylinder in my old car due to water in the system.

Mainerider
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Re: Brakes

Postby Mainerider » Tue Jun 04, 2013 10:55 am

canuck1sailor wrote:Is there a gasket between the MC lid and the reservoir? (1980 CB 650 C with 4 bolt reservoir lid) The manual shows that there is a gasket fitted; however the reservoir kits don't indicate a gasket is included. Mine does not have a gasket, it now leaks after cleaning and flushing. It did not leak prior to cleaning and flushing and the brakes work well as they did before.

Any ideas?

I was concerned about the age/condition of the brake fluid having just replaced all brake cylinders and master cylinder in my old car due to water in the system.



Honestly, stop wasting your time and money on trying to salvage a 30 year-old component; In my experience the rebuild kts are typically useless because the bore wears and pits as well, and the rebuild kits don't address that problem. And yes, there is a rubber o-ring that can be purchased for under the reservoir bowl; However, I've found that the MBC will still weep around there afterwards. Plus it is very difficult to remove, without damage, the plastic cup from the body in order to replace the o-ring; it is, naturally, fitted on there extremely snugly.

You can purchase a new, aftermarket replacement master cylinder for your bike on Ebay for about $50. I've installed several on the bikes of customers and also on my own bikes and they work and look great, great enough that I purchased 2 spares and have them in my garage as we speak.

Here is one example... http://www.ebay.com/itm/Honda-CB-Brake- ... 1e&vxp=mtr

Also, as mentioned, you need to service the caliper as well; that is the low spot of the brake system and naturally the mosture collects there. Addressing the MBC while not cleaning the caliper is mostly a waste of time.
Last edited by Mainerider on Tue Jun 04, 2013 11:17 am, edited 1 time in total.
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canuck1sailor
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Re: Brakes

Postby canuck1sailor » Tue Jun 04, 2013 11:17 am

Done. Thanks.

canuck1sailor
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Re: Brakes

Postby canuck1sailor » Mon Jun 24, 2013 1:45 pm

I have a stainless steel brake line for my 1980 CB650C on the way. Single disk brake.

Do I need to fit the protective rubber sleeve that was on my original rubber brake line?
I'm wondering if it is needed to prevent the s/s line chafing the other cables; wires and suchlike.

Also one of the hold down clips directs the brake line to bend at a 90 degree angle to the left then down to the left fork. Is this the correct routing? Or can I just make a gentle curve down to the calliper?


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