Front brakes are mushy, what should I try?

[chuck c]

MS is off. I need to get snap ring pliers. How does the reservoir come off? It will turn but doesn't pop off and I'm not going to put too much force on it.

 

[zman]

That little snap ring is a tough one, I bought a special tool from motion pro to remove mine, the reservoir is no less difficult and needs to be pried even with a tool that wont gouge the plastic, can you maybe leave the reservoir on?..I think you can rebuild with it on unless the oring is leaking I would leave it alone.
I`ll tell ya, I bought a 30 dollar Chinese M/C on Ebay 4 years ago and was going to rebuild my original but the cheap one is working real nice so the old one is still apart, the rebuild kit cost more then the new M/C did.

 

[chuck c]

With much taking of the Lord's name in vain I got the snap ring out and all apart. Rebuild kit ordered. We'll take this back up next week.

 

[joedrum]

glad you got it out .....

 

[OldWrench]

I have an 83 so brakes are a little different. Right after I bought this bike I went through the brakes. When I went to rebuild the MC I found that the cylinder had corroded and there was no way to get a clean bore, so I replaced the MC with new that had an oversize piston and it works great, the 83 hand brake only operates on caliber and I think I could lock the front tire if I tried to but that isn't a good idea, point is it give me plenty of stopping power. Lots of good advice here on how to bleed the system.

I agree with Dan, the whole system hast to be right. As for Orifice size, controls flow only, not pressure, basic hydraulics. If the orifice is restricted the MC may not be able to deliver enough fluid for adequate braking, but it shouldn't have any effect on spongy brakes, that is almost always air. If a MC seals are bad the fluid can bypass the seal and also cause a spongy pedal or grip.

 

[OldWrench]

Chuck, get yourself a small 90 degree snap ring pliers, will make your life much easier, also make sure the MC bore is smooth and clean.

 

[chuck c]

OldWrench » Wed Jul 06, 2016 8:47 pm[/url]":30mdfiiv]
If a MC seals are bad the fluid can bypass the seal and also cause a spongy pedal or grip.

I really think that is the problem. I'm pretty darned sure I got all the air out. The seal is probably the original from 1981 and it's been sitting for 4 years. It's just not able to hold the pressure anymore. It's just time to do it. The kit will be here in a few days. None of the local shops had it in stock. Can you believe that? Not stocking parts for a 35 year old bike? {sarcasm}

I saw a video of a simple reverse bleed method similar to the one described earlier in this thread. The guy used a huge syringe to force fluid into the bleeder and up to the MC. Nice because the caliper stays in place, no messing with a C-clamp on it to force it back. I'm going to see if I can my hands on one of those and try it.

I tried to get the reservoir off with enough pressure to make me really nervous and gave up. I need to repaint the body and it would be easier with it off, but noooooo. I was able to make sure the return hole was clear. It looked pretty good inside.

 

[mcgovern61]

Popping the reservoir off is a pain! I twist mine while prying from underneath. It is a bugger. It is also a lot heavier duty that it appears!

 

[Denver]

Yes that rascal is sometimes pretty tuff, :whistling: BUT it comes off, :yes: & a new Oring is going to be necessary to seal all of the pressure. :good: If not now, you will need to later, :roll: or you won't be satisfied with the brake's performance. :nea:

 

[chuck c]

WOOHOO! The kit came today! I can ride tomorrow! Well, maybe. If I can put it back together right. Does anyone have good clear exploded view? I think I know, I did pay attention as I took it apart but I'd really like to have a pic.

 

[chuck c]

uh... the cup seal that's on the piston. It is NOT on it in the rebuild kit. How am I supposed to get it where it needs to be without damaging it?

 

[Denver]

There tuff, :yes: just don't get it on backwards. :Awe:

 

[chuck c]

Well, I messed that up. All together, on, bled from the bottom up, and LESS pressure than it had before. I put it together wrong. I should have waited until I had the info instead of relying on memory.

 

[OldWrench]

What do you mean by put it together wrong? Also, is the MC bore smooth and clean?

 

[chuck c]

The bore looked ok. I mean I must have put it together wrong because it has zero pressure and I can't see any other reason.

 

[slabghost]

Even new master cylinders need primed. Take the line off the master. Fill with fluid and cover the hole where the line goes with your thumb. Now pump the master slowly until it squirts fluid past your thumb on squeeze and tries to suck your thumb in on release. Then put the line on almost finger tight. Squeeze the handle until the fluid is leaking past and tighten the banjo as it does. Top off the master and then see what you have.

 

[joedrum]

sheesh just slow down and gather yourself ...it not that hard a thing ...one of the biggest problems on oldwing work is sometimes things are not taken far enough to determine there good or not ..and assume bad ...next time work with old stuff till you know what wrong completely ....before throwing new parts at it .....

 

[OldWrench]

I've always had a personal rule, if a project gets me totally frustrated, walk away, have a beer and think the problem through. Joe is right, throwing new parts at something hoping it will cure the problem without first knowing exactly what the problem is can get real expensive and frustrating.

 

[chuck c]

I was very tired and frustrated when I posted that last night. My head is a bit clearer now. It's likely there's still air in the ms. I will go through the drill to be sure it's full and primed. It is still possible that I didn't put it together correctly but I haven't eliminated all other possibilities yet.

I'm basing all this on the last time I put a master in a car. It was no sweat. I filled it with fluid and pumped it a few times and it was ready to bleed. It primed itself. That's why this is getting under my skin. I didn't expect a simpler system to give me so much grief.

 

[chuck c]

I used an old brake line off the parts bike which I highly recommend having if you can. I put it on the master and put the end in the reservoir, then pumped the lever until I had good fluid and no bubbles. It was a very simple way of priming the master. I clamped off that line and the lever is rock solid unmovable. That means I did put it together right. The old one might have passed that test but I don't consider the rebuilt of a possibly 35 year old master a waste of time or money.

I found a great tip online last night. Isolate the master and calipers by clamping the hoses with vise grips and a piece of cardboard to protect them. After switching back to the real brake line I repeated the clamp-off test to see if any air got in while I was switching. Still rock hard. One down, two to go. That only works with rubber hoses, braided steel ones would be damaged.

So then I clamped each side off while I bled the other. I had a feeling I have been chasing a bubble from side to side. I used both methods: reverse by forcing up from the bleeder valve and old fashioned open-squeeze-close-release. This made a huge difference. Both sides are strong enough to roll the bike out and try. I will do that after I have a snack. I make bad decisions when the old blood sugar is low. :doh:

The lever is still a bit soft but I'll blame the old hoses. Hose replacement is on the list for a later project.