Rear master cylinder rebuild

[cmonSTART]

I have used small wire wheel attachments for a dremel in the past. They work OK but you only really get 1 or 2 uses out of them.

 

[dan filipi]

I had one apart a year or so back but I can't remember if once the spring clip is out the cupped washer and piston come out.

I have the spring clip out but the piston (and washer?) won't come out.
Is there something I'm missing?

I have it soaking with PB Blaster.

 

[AApple]

If it's anything like an automotive cylinder, once the clip is out, the piston/rod should come right out....unless the seal is swollen up quite a bit, then you might have to work it around a little. If all else fails, skwert some air in the other end...and make sure you got it pointed away from everything....

 

[scdmarx]

My guess is a ring of corrosion build up where the piston stopped. I suggest the pb balster and like mentioned before apply air into the other end if you can.

 

[dan filipi]

Ok, got the piston out after letting it soak for awhile.

Although the cylinder looks nasty it feels smooth further down where the seal needs to happen.

View media item 6180
I'm afraid I'd do more harm than good using anything on it.

I'm going to pick up a couple dremel wire wheels to clean the spring clip groove and down inside here unless someone has a better suggestion.

View media item 6182

 

[mcgovern61]

When I did my rear MC, I cleaned it with aluminum foil and it worked real well! Not too tedious and little chance of gouging the insides.

 

[dan filipi]

When I did my rear MC, I cleaned it with aluminum foil and it worked real well! Not too tedious and little chance of gouging the insides.

How did you do that?
I can't even get my pinky finger down in there all the way.

 

[mcgovern61]

I used a large flat headed punch (about 3/8" wide at the tip) and wrapped the tin foil around it. The flat bottom of the punch was small enough that as I rotated the punch and tin foil, it (for lack of better words) scrubbed the bottom clean all the way into the corners and came out nice an shiney!

 

[joedrum]

:good: :mrgreen:

 

[dan filipi]

So far I've managed to get the trashed brake line out but that meant removing the line going to the front brake then found out the hex of the old line there too was rounded out and no way to get a vise grips in there to get it off :head bang: so I had to remove the rear line which was chewed up also :head bang: .
With more strategic placement of the jaws of life that line is off.
So now I have the equalizer valve out.
Next break in the rain I'll pull off any reusable hard lines from the parts bike, any I don't have my buddies at All Car Parts can make up.

 

[dan filipi]

I want to do up this cylinder right.
You'd never tell with all the mods I've done on my bike but I'm pretty anal when it comes to brakes.

I'm having trouble finding a hone for 5/8" diameter.

Any ideas where I can get one?

 

[dan filipi]

I found this one, will it work?

https://www.sjdiscounttools.com/brmbc5-8.html

Would be nice to find one local pick up though.

How can I tell if 5/8" is the right size I need?
I measured the bore but I can't get down very far, not as far as where the seals ride.
Is there maybe a usual tolerance on the seal, maybe measuring the new seals?

 

[scdmarx]

According to specs, 5/8" is just under 16mm, so that would most likely be the size. But in my opinion, unless you're trying to clean up some really stubborn gunk, buying a hone is overkill. I don't think you're supposed to hone this (as in "take away metal") The rubber cups expand as the fluid applies pressure.

With no way to measure like the manual says, I'd just clean it up and go with a new kit if all looks ok.

 

[joedrum]

me too ...like ron said :mrgreen:

 

[AApple]

You can get a dingleberry tree(flex hone) at any automotive parts house, if you need one. Prolly cheaper than the one you linked to...and no shipping. :mrgreen:
Get some fine sandpaper(200-400 grit) and wrap around the hone and run that up/down a few passes, instead of using the bare hone stones. It'll still clean up the bore without removing very much of the bore metal. If that doesn't clean the bore up nicely enough to run, then you prolly need another cylinder.
You could also use some Scotchbrite pad(the red works for me), and spin that down in the bore to smooth it up a little, for the final pass.
Just throwing ideas out there.... :mrgreen:
I'mma gonna have to go thru my rear cylinder soon, too....hope mine ain't as hard as your's has turned out to be! :beg:

 

[toytender01]

I just kitted 3 cylinders... I used steel wool to polish up the cylinder and pistons.. worked great :Egyptian: :Egyptian:

 

[dan filipi]

Problem I have with the rear master is getting into it.
The barrel is only 5/8" diameter by about 3 inches deep so there's no seeing inside or feeling if it's smooth.

I might just take the advise to leave it alone and just the new parts in. I'm afraid of damaging the surface.
I'd take a chance if these were available new.

 

[slabghost]

You could use a brass bore brush for a 10 or 12 guage shotgun.

 

[dan filipi]

Good idea V.

 

[dan filipi]

Got the wheel cylinder done :clapping:
I'll try to get it back in the bike this week.

I was going to do up a how to but it's all pretty straight forward, hardest part was digging out the crud where the dust boot sits and the groove the snap ring goes into.

I decided to leave the barrel alone since the cupped rubber washer was noticeably smaller and hard from age than the new one.
Hope it don't leak.
If it does I'll be looking for a retro MC.