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Discussion Starter · #1 ·
Well, at first I thought that my master cylinder was leaking, and I still think it is (a little) but I was focusing on that so much that I forgot to look down. I just noticed that it is actually the caliper that is leaking the most. I am losing brake fluid from it and cant tell exactly where it is coming from because it is all pretty wet down there. What do you guys suggest. is it easy to rebuild? or should I get a new caliper? Are there any quick fixes to this problem? If rebuilding is suggested, where is a good place to get a kit? TIA



cody
 

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I would first take a bucket of soapy water and wash and rinse the caliper off. Then after it dries, you may be able to tell where the leak is occurring. You can also dust a little flour on the banjo bolt and the bleeder screw and that may help identify if the leak is at either of those spots.



If the banjo bolt is leaking, you may need to replace or anneal the crush washers on either side of the fitting. Best to replace them, they should be a auto parts store item. To anneal, just heat them up to glowing and then let air cool. Don't water douse them, just leave them lay till cooled. This will restore the malleability of the washer and allow it to soften and seal properly.



If it is not either of these spots, you will need to remove the caliper and push the piston out before you disconnect the lines. Just remove it from the forks and start pumping with the lever. Have a pan underneath to catch the fluid when the piston finally comes out. Reach into the bore and extract the square O ring from the groove. Be a little careful, you don't want to gouge the bore with a sharp pick. With the O ring out, examine it, and using your finger nail scratch off any deposits from the ring. If it is chewed up, or brittle you will have to replace it, but generally it can be reused.



Now take a curved dental pick or equivalent and get all the gunk out of the groove. That means all parts, including the front surface that is hard to get to and see. The condition of the O ring and groove is one component of allowing the pads to retract from the rotor. Don't scar or round out the groove, but get it clean.



Clean up the piston if necessary with 0000 steel wool and polish it if you want to. Any surface pitting that is at or below the O ring seal on the piston must be removed or a new piston ordered. Pitting to the outside of the O ring really doesn't hurt anything.



Coat the O ring with brake fluid and fit it back into the groove. You will think at first that it is too large, but once you get it positioned, it will be fine. Then lube the piston with brake fluid and carefully align it in the cylinder. Open side out! You should be able to now squeeze the piston back into the cylinder completely. It may take some twisting and realigning, but thumb pressure is all that is needed when everything is lined up.



Lube the mounting pins and bolts and reassemble to the forks. Then bleed the system and check for leaks. Total job should be 2-3 hours at most.
 

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tighten up the banjo bolt and the bleed nipple - then wash it down and look for leaks

no need to rebuild - unless fluid is coming from the piston seal area. the last post is correct if you want to rebuild anyway.

did this just happen or have you been playing with the brakes??

is the fluid on the brake pads - if so you may need to replace them as well.
 

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Discussion Starter · #4 ·
There is no fluid on the brake pads but its all over the bottom of the caliper. About 2 months ago the brakes started getting kind of mushy, I thought it was just air and didnt think much about it. Eventually the lever would just pull right back to the grip with little to no resistance, when I checked the reservoir it was empty. I put some fluid into the reservoir up to the fill line and let it sit over night. The next morning the lever was nice and firm and stopped like a charm. Then after a few weeks, started feeling mushy again and in no time there was no resistance...again. So I have just been refilling the reservoir which has been working for now, but I cant just keep dumping fluid in. I thought it might be the master cylinder at first but I didnt find any leakage there, it was a little moist however. But when I bent down and checked the caliper, there was fluid all over the bottom of it. The bleed nipple and the banjo bolt are both dry so I dont think it is that. It looks the most wet directly at the bottom of the caliper so Im thinking that it needs to be rebuilt. I would take a picture but I dont have my camera with me right now but as soon as I get it I will put one up.



cody
 

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Cody,



Here is a link to another member's webpage. I found the pictures and instructions very helpful. Your 78 probably has a sinle piston caliper. It's the same idea, except it's one big piston instead of two smaller ones.



Ofapars
 

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check your brake line near the caliper - is it wet with fluid - it could be leaking down the line on the outside - then finding its way to the bottom of the caliper...

wipe the whole brake line over - try and find if it is wet along some part of its length.



IF the master cylinder is leaking -I would suspect it from what you have mentioned - is it leaking around the banjo bolt or around the bottom of the reservoir? I presume you have a plastic reservoir ?



You might be real lucky if the brake fluid has not contaminated the pads -
 

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Discussion Starter · #7 ·
check your brake line near the caliper - is it wet with fluid - it could be leaking down the line on the outside - then finding its way to the bottom of the caliper...

wipe the whole brake line over - try and find if it is wet along some part of its length.



IF the master cylinder is leaking -I would suspect it from what you have mentioned - is it leaking around the banjo bolt or around the bottom of the reservoir? I presume you have a plastic reservoir ?



You might be real lucky if the brake fluid has not contaminated the pads -
When I said earlier that the pads were dry, I was thinking in my head "Rotor" not "Pads". The rotor does not appear to have any oil on it, however I have not taken the pads out to check. I assume that the pads are dry because the rotors appears dry but I should look at that to figure out for sure. I checked the line again and I cannot see anywhere that there is oil on it, but Im going to wipe everything down real good and then see what happens. I already ordered a rebuild kit for the caliper that should be here in a day or two so I will have it on hand if I need it.

My master cylinder is the metal one, the whole unit is molded together and the lever attaches to it. I will double check the banjo bold on the MC too just to double check. I feel like I just need to cover all my bases on this one.



Thanks for everything



cody
 

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Whether or not the brake caliper is the culprit of your brake fluid leak, rebuilding the caliper is vital. Remember that your bike is over 30 years old now and a properly functioning front brake is crucial to keeping away road rash.



Your brake fluid leak may be due somehow to a crush washer. At each end of the brake hose is a banjo bolt. Each end of the hose should have two crush washers, one on either side of the banjo bolt (4 total on your bike). If one washer is missing, you'll get a fluid leak for sure. Sometimes the washers have no more "crush" left in them. In that case replace them or anneal them.



Next, seriously consider replacing the brake hose. They're not cheap but again, your bike is over 30 years old. I think they're around $40.
 

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Discussion Starter · #9 ·
Yeah, I figured that I have the rebuild kit coming so I may as well use it. Ive been looking at steel braided lines so as soon as I can afford that I will order it. I have not checked the crush washers but when I take the caliper off to rebuild it I will check them out and see if there is any damage to them, or just replace them all together. Can you pick those up at an auto parts store (Advanced Auto, Auto Zone etc.)?

Now I just need to put some higher weight oil in my forks and I should be good to go (as far as safety issues go anyway). They almost bottom out when I sit on the bike and it makes it pretty unstable, and VERY unstable at slower speeds.



Cody
 

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Take the whole system off the bike, strip it down completely and see what damage has been done with age.....replace EVERYTHING and it will be good for another 30 years...nothing last forever, I say 30years is BRILLIANT for any machine...but at sometime it will fail.
 

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Regarding the copper washers, any motorcycle shop ought to have them. I don't know about Autozone, etc.



Are either of your fork seals leaking? If so, replace the seals. They are cheap -- I paid $15 for mine that I haven't installed yet. Been busy. But yeah, new seals and the proper amount of oil and it'll seem like you have a new bike.
 

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if the fluid is leaking out primarily at the bottom of the caliper there is a capped off hole that is capped with a small allen screw on the underside of the caliper. i suspect the left side and right side caliper housings are interchangable and the unused hole is capped off. that might be the source of the leak if no others are apparent. good luck! i just had so much fun with my caliper rebuild i was wanting to punch a party clown.
 
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