Topic: Gummed Up Brake Master Cylinder

[phrige]

Hey I was wondering what you guys would recomend, I'm rebuilding my front brake master Cylinder on my '75 Honda cb550.

 The ring clip-circle clip thing is pretty junked up in there. I've let it sit in boiling water for some time, then poured some into the end of it, to clean out the gabich thats living in there. It's mostly out but I think the clip maybe rusted onto the piston.

 I'm wondering if its safe to use LiquidWrench or a WD-40 in there, to loosen this guy up. It's a tough reach with my ring clip pliers.. I even grinded down the sides of the plier ends so it could reach down deeper without hitting the walls of the cylinder, no dice. gatta get some awls.  Anybody got any other tricks to it?

[BeSeeingYou]

Be aware that there is probably a wire c clip that holds the boot on and then the main c clip that holds the piston in. You should be able to get the wire clip out with a small screwdriver or pick.   If you do a search you will find a few ways to get main c clip out by using awls, picks, modified needle nose (I did that one) but for $10 you can get the proper deep reach tool from www.Mikesxs.com
    It helps if you find some way to hold the piston down to take the pressure off the c clip.   WD 40 or some type of penetrating oil should not be a problem.  Like I said do a search and you will find plenty of advice about this.  It seems we all have been there at one time or another.

[Doctorlumen]

+ 1 on the "proper" tool for the job. Motion Pro sells one, but it is probably a bit more than $10.

When I did my 400 four's brakes, they were in (it sounds like) similar shape. I used WD-40 to brake everything loose, and as a general cleaner, but prior to final assembly I went over everything with denatured alcohol to get rid of any oil residue. Then I lubed the master cylinder and caliper piston bores with clean brake fluid. Hope this helps!

[octagon]

if you don't care about the clip, put the cylinder housing in a vise (carefully) and use a thin punch and a light hammer on it. strike the middle of the clip, equidistant from the two ends, several times. don't use too much force. it may take 8 or 10 blows. the idea is to hit the clip not the cylinder housing. eventually the clip will deform and pop out. then throw it away.   

[phrige]

I went the punch method. (Thanks for that advice)

and after a lot of finesse work I removed everything. It was certainly an uphill battle as everything was Royally rusted in there. Nothing wanted to move out. Yet the spring and cyclinder in general worked ok not the best but still worked.

Now my problem is, When punching I managed to damage the lip a little bit in two places. I was having trouble getting the washer out so I punched that to have something to grip with. I did it in a few places but 'struck' twice. One's more severe than the other.

Will this essentially render the master cylinder unusable?

I don't have my camera + its too dark to take pictures right now anyway.

[Alan F.]

so the area near the circlip groove is a little damaged? will the new circlip be able to lock into the groove? if the damage doesn't go very far past the circlip groove I wouldn't worry much about it, have a look at the piston and you'll get an idea of how deep you'd have to go to render the m/c useless.  smooth the damaged area with some find sandpaper and proceed with your rebuild.

[KingCustomCycles.com]

The piston seizes from corrosion BEHIND the seal in the groove, not from gunk and rust on the piston or in the bore.  Clean the sealing groove very thoroughly with a piece of soft aluminum or a mild scraper of some kind.  The corners are especially important.  I have even reinstalled the old seal it this point with no problems. 

[phrige]

So here are a few pics to really show the damage.

I'm thinking it maybe a little far gone, though I haven't sanded it down at all yet.

Let me know what y'all think.

[lrutt]

I would strongly recommend pulling the caliper off and cleaning it as well as it will have that crap in it too, flush the lines with brake cleaner. I'd also take that opportunity to convert to DOT 5 fluid. You won't get that gunk build up anymore and DOT 5 won't eat your paint. I've done that to all my bikes years ago and have eliminated gunk build up in my brake systems. That gunk is from DOT 3 absorbing moisture. DOT 5 won't do that, it's silicone based.

[phrige]

Nice,

  Yea I got a full rebuild kit, so I'm ganna shine up the inside of this guy as best as I can. If its worth it that is. I'm on the fence about it. I'm probably better off just spending a couple bucks on a new MC instead of worrying about the integrity of this one.

 Though it seems like it would work for a while.  
 
 Thanks Irutt about bringing up the point about the brake lines. I forgot that they're probably pretty grungy inside too.

  BY the way. This maybe another symptom of this whole mess. When I went to drain my brake fluid inorder to get the MC off. I wasn't able to get anything to come out of the bleeder. I unscrewed and pumped. unscrewed and pumped more. Basically I ended up unscrewing the whole thing, I believe the brake fluid just leaked out from there then.
 ??Clogged Bleader screw?? Hope its not the whole front brake, it worked alright all together albeit sluggish


 

[octagon]

you have to use your own judgement, but if that was my master cylinder i'd smooth out the damaged place carefully with a round file, then clean the bore and use it. that's assuming there's no damage further down the bore from corrosion or whatever.
and as lrutt says, you've got to take your caliper apart and clean it. lots of info on that if you do a search.
the caliper bolts have 8mm hex heads. if you put the caliper in a vise, you can use a hex bit socket, a breaker bar, and say a foot of cheater pipe. you can lean into that setup and apply a lot of force smoothly. i found that to be a good way to get the bolts to break loose.
   
 

[phrige]

Nice, thanks.

The caliper is ganna be my next project.