Topic: Whats the second hole in the master cylinder for?

[newcbguy]

As I was struggling with the rusted circlip in my master cylinder, I noticed 2 holes in the resivoir. one goes through for the brake fluid and the other only goes down about 1/4" and seems to stop. Is this a safety bleed hole like a buddy of mine suggested? Maybe it is just a tiny hole that is still plugged up? Im puzzled on this one but plan on taking a dental pick to it to search for a smaller hole recessed in the larger one.

[Bob Wessner]

the other only goes down about 1/4" and seems to stop.

Assuming the hole is not blocked, take it out in the sunlight or other bright light source down the bore. There is a v-e-r-y tiny hole at the bottom of that drilling. If you don't see the hole, it has to be cleared for the brake system to function properly.

[newcbguy]

I expected that it was there for a reason. The only other explanation I had was maybe the machinist was a little woosey and missed the first time he drilled! I will take another look this evening and make sure that hole is cleared. Thanks!

[BobbyR]

Get some denatured alchohol and clean out all  the junk in there. The stuff will not harm the parts since it is the major chemical in brake fluid.

[Killer Canary]

It allows air to bleed out of the system. If the hole is blocked, the piston won't release the disc. Use an 11 thou guitar string.

[newcbguy]

Ok, I got the hole cleaned out, now there is a new problem. I let some brake fluid sit in the reservoir overnight/today and it is leaking from the piston behind the lever. thats not a good sign I take it. I am pretty sure that it rebuilt it correctly, is there anything I should look for?

[TwoTired]

I rebuilt a master with new parts that did that.
Turned out there was crystalized brake fluid hard coating the cylinder wall, making it out of round.
I used a wooden dowel, cut a slot on the end and then inserted fine emery paper into the slot.  Chucked it in a drill press, and honed the master cylinder.  A strong light and and a small inspection mirror told me when he glazed was gone.  Reassembled, and the leaking stopped.

Another thought. Did you put the new seal in correctly midpoint on the piston?  It's a tortuous stretch.  But, thats where it goes.  The parts diagram doesn't show it installed, just "associated".

Cheers,

[Bob Wessner]

Another thought. Did you put the new seal in correctly midpoint on the piston?

From experience , I can tell you the symptoms of not doing it this way are just as described for your new problem.

[newcbguy]

two tired, I pulled about 20 parts out of the master cylinder and a pile of goo, but i didnt notice that the seal was around the piston. that would explain it. i put it in just like the exploded diagram shows. that means I get to take the circlip back out I guess.  Thanks for pointing that out though!  I was about to start looking for another one to rebuild, but I will try that first.  I too used some 600 grit sandpaper wrapped around a pencil to clean out the old crust inside the piston hole, but I didnt want to get too carried away with it so as not to make it leak. Funny how that works huh?

[newcbguy]

It sure is easier to work on that master cylinder when the parts are clean and you've got some experience! I just rebuilt it again in about 20 minutes. I put the seal in the middle of the piston and it seems to be working now. Wonder why they dont point that out somewhere in the manual? Thanks for the pointers though!

[Bob Wessner]

Wonder why they don't point that out somewhere in the manual?

In reality, I think they do. That's what that bracketing/joining set of lines means on the diagram. Unfortunately, it requires one to interpret it correctly, which I didn't a couple of years ago and suffered the same symptoms and redo myself.

[BobbyR]

Chysyalized brake can be washed with denatured alcohol.

[GoatBaSS]

It allows air to bleed out of the system. If the hole is blocked, the piston won't release the disc. Use an 11 thou guitar string.

X2

[stresssolutions]

Sooooooooooooooooooooooo how do you get the snap ring off the MC??  We've tried a number of things, and the clip is not stuck....it will rotate around the groove.  Anyone got a special tool they'd loan me?  Anyone want to volunteer to rebuild it for me?  I've got the kit....would pay shipping........

Thanks for any tips or pics...etc.

[BobbyR]

If you have a string dental pick or thin probe you can lever it out. If you can one end out of the groove you can usually get something thin  behind it and pop it out.

[Sam Green Racing]

Piiinnnnnggggggg.............now where the fcuk did that go Bobby

Sam.

[754]

 I bought a HAZET tiny snap ring plier, should fit in there but yet to try it out.. look for tiny needlenose like tips, not changeable end ones.

[newcbguy]

I used a pick with success as my snap ring pliers would not reach all the way down into the cylinder. I just pried the ring towards the center of the hole a few times and finally it caught and popped out of the groove. carefull, It will fly across the room! to reinsert put the ring as far down as you can with your insufficient snap ring pliers and then push it back and forth with a small screwdriver and or the pick. It does help to compress the piston a bit to ease the tension on the bottom surface.  (I have learned this by doing it about 4 times - dont ask)   

[stresssolutions]

It does help to compress the piston a bit to ease the tension on the bottom surface. 

I got my wife to help me last night, but we did not have success...yet.  we were compressing piston trying to garner more room for the pliers, but of course the screwdriver we were using gets in the way, not enough light, ever, can't see in there with fingers and pliers in the way.  May clamp MC back onto the bike, so it is securely held and get the piston down and secured somehow then pick away.  Need to find a dentist to help me, I think.

[upperlake04]

 For a tool I will use only a few times at most, my solution was to dig a small cheapy  needlenose out of the bottom of the toolbox and spend 5 minutes on the grinder.  It worked well

[kirkn]

Yep, I've made "dedicated" tools out of 1.95 tools & a grinder.  I've also used hardened concrete nails and ground a snap-ring tool type point on the end.  Gives a longer reach to your ordinary snap ring pliers.

Kirk

[BobbyR]

I put the MC in a vise, used a piece of tongue depressor to pin the piston as far down as it would go for clearence.

[754]

I DID IT!!

 Finally tried out the Hazet split ring pliers

1846a-0

 Works like a hot damn!! even could go deeper..
 Man was that easy. . well worth it..

My dealer has one left at 38.50.. and are no longer carrying that brand.

Apparently there is a part # for a Honda one in some manuals. anyone know what they look like??

[05c50]

If all else fails, Motion Pro makes a set of snapring pliers for just this job. cost about $23.00. Z1 Enterprises sells them. You may not ever use them again,but your sanity may be worth $23 bucks. Besides everyone knows"the man that dies with the most tools,wins"

......Paul

[754]

I will have to take a look, the Hazet probably kicks the Motion Pros Ass.. German engineering  you know.. JA!!!