Front Brake

[bul_racer]

Thought I'd clean out my front brake and rebuild it. New seals in MC and caliper. I've read many of the posts on this subject and tried to follow the procedure recommended by gggGary. Removed caliper inserted piston just enough to hold it in place then filled with fluid. Attached C clamp on the piston & closed until fluid came out of the hose opening.
Some bubbles but not a lot.

Filled MC with some fluid but not full to top. Pumped lever with finger over the exit hole & it pushes fluid out but not impressive flow. Might have made a mistake by not priming the MC?

But it does push fluid out so I attached the upper hose, pulled lever to handlebar & taped in place overnight. Then I held fingers over lower part of upper hose while pumping lever. Fluid is expelled but, again, not at an impressive rate. Put finger over lower opening in the middle box & squirted fluid into the box till it came out the top. Then connected lower part of upper hose to the top of the box, still holding finger over lower opening. Connected upper part of lower hose, then holding fingers over lower end pumped lever till fluid comes out the end. Still, not impressive flow. Next connected lower of lower hose to caliper. Worked lever but no resistance.

Tried taping lever to handlebar & leaving overnight to see if any bubbles would come up. Don't think any did. Pumped lever with bleeder open. Small amount of fluid & bubbles came out on first 5 or 6 pumps but after that it did not seem to be moving. Opened bleeder & left overnight but no difference.

I hooked up a syringe to the bleeder valve. Syringe directions say to clamp lever to handlebar and then use suction to draw fluid out until all fluid is replaced. However, fluid does not move into the syringe. Tried pushing on the syringe but that didn't work either, as fluid was not accepted.

At this point I'm not sure what else to do. Maybe take MC apart & make sure it's primed. I didn't mention that I've pumped that lever at least 1000 times. I don't mind doing that & wouldn't mind doing 5000 if it would eventually make it right but I'm not sure it would.

One thing that's quite annoying is that without the top on the MC it leaks fluid from the bottom of the white plastic part of the MC, even with screws in to hold it down. My garage floor is getting a brake fluid bath...

Any help is appreciated.

 

[Vincenthdfan]

I have one of those cheapy air compressor operated vacuum bleeders from Harbor Freight (not the hand operated jiffy pump).

I just rebuilt two separate 1980 Special's brake systems front and rear and had zero problems bleeding any of them with this bleeder.

Worked immediately. No priming, no pre-bleeding...nothing.

Now, having said all that...I did have to replace all of my hoses because they were all degraded and clogged internally...tried bleeding without swapping hoses and had minimal success and the brake pressure wouldnt subside after pedal was released (trapped pressure/fluid).

Also, theres two separate holes inside the master cylinder reservoir...one little bitty one you can barely see. Its notorious for clogging...make sure its clear too.

 

[bul_racer]

I have one of those cheapy air compressor operated vacuum bleeders from Harbor Freight (not the hand operated jiffy pump).

I just rebuilt two separate 1980 Special's brake systems front and rear and had zero problems bleeding any of them with this bleeder.

Worked immediately. No priming, no pre-bleeding...nothing

Now, having said all that...I did have to replace all of my hoses because they were all degraded and clogged internally...tried bleeding without swapping hoses and had minimal success and the brake pressure wouldnt subside after pedal was released (trapped pressure/fluid).

Also, theres two separate holes inside the master cylinder reservoir...one little bitty one you can barely see. Its notorious for clogging...make sure its clear too.

Vincent,

Thanks for your comments. What's your idea of cheap? I see one on Harbor Freight website for $100. Not exactly my idea of cheap but I'm a tightwad. There are cheaper ones but they're hand operated.

My original hoses seem OK but I don't know how to tell for sure. Any ideas on that? I suppose that could be my problem. I just can't figure why I can't force fluid through with both ends open. I've been suspecting the little midway box but I really don't know.

Not having a problem with pressure building too much. I'm not getting enough.

Question: I only see the 1 hole in the MC. Can you say where the small one is in relation to the bigger, visible one? I'll look closer & maybe I'll see it.

 

[5twins]

I would replace the lines. I always do that, very rarely rebuild the caliper or MC, just thoroughly clean them out. Stainless lines are dirt cheap on eBay, less than $10. Most of us get one long line to replace the original two and that splitter block. For slightly lower than stock bars, a 90cm (about 35.4 inches) line length works perfectly.

 

[miketweedie]

This may or may not help you, but when bleeding the brake MC on his MX bike, my buddy swears by using his Theragun (you know, those massage guns that help with sore muscles?) The high-frequency of the vibration helps knock loose all the trapped bubbles, and it works super well. I suppose any similar device could work, though you'll want to be careful not to use anything that could cause damage.

 

[gggGary]

You rang?
Might want to review my method and do it completely.
"I like the patented gggGary brake bleed technique; slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line. NOW with port pointed up push in piston til fluid shows in master cylinder reservoir, top off reservoir, done. You can pump out piston, squeeze back in an extra time or two if needed. But usually once n done."

that whole tie the lever to the handlebar thing is a legend, and is of no particular use.
But what do I know? I've only R&R'd 30 -or 40 front brakes.
I'll go hide now.
It is a thing for OLD brake lines to become so soft and or start shedding rubber bits internally, as to be completely useless/dangerous.

 

[joebgd]

I had a similar problem. Plenty of pressure w my finger over outlet of mc. No resistance when brake is hooked up. I wound up taking it to a shop. I tried everything you did. I would trust the experience and try w the port upwards. I never did that it was always lower on special pull back bars. I think the shop used a vacuum pump. The hand held ones work fine from what I've read here.

 

[Mikey]

You rang?
Might want to review my method and do it completely.
"I like the patented gggGary brake bleed technique; slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line. NOW with port pointed up push in piston til fluid shows in master cylinder reservoir, top off reservoir, done. You can pump out piston, squeeze back in an extra time or two if needed. But usually once n done."

that whole tie the lever to the handlebar thing is a legend, and is of no particular use.
But what do I know? I've only R&R'd 30 -or 40 front brakes.
I'll go hide now.
It is a thing for OLD brake lines to become so soft and or start shedding rubber bits internally, as to be completely useless/dangerous.

"slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line"

When you put on the line as above do you fill the line too from the top end ?
And do you have the slave cylinder mounted on the bike ?

 

[bul_racer]

I would replace the lines. I always do that, very rarely rebuild the caliper or MC, just thoroughly clean them out. Stainless lines are dirt cheap on eBay, less than $10. Most of us get one long line to replace the original two and that splitter block. For slightly lower than stock bars, a 90cm (about 35.4 inches) line length works perfectly.

View attachment 250900

Yeah, I'm thinking of going with just 1 line. Haven't checked ebay for stainless. When I looked on Mikes I thought they were pretty expensive. I'll have to measure since I changed to a lower bar. Thanks for pitching in.

 

[bul_racer]

This may or may not help you, but when bleeding the brake MC on his MX bike, my buddy swears by using his Theragun (you know, those massage guns that help with sore muscles?) The high-frequency of the vibration helps knock loose all the trapped bubbles, and it works super well. I suppose any similar device could work, though you'll want to be careful not to use anything that could cause damage.

Great Idea! I have a similar machine I can try.

 

[bul_racer]

You rang?
Might want to review my method and do it completely.
"I like the patented gggGary brake bleed technique; slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line. NOW with port pointed up push in piston til fluid shows in master cylinder reservoir, top off reservoir, done. You can pump out piston, squeeze back in an extra time or two if needed. But usually once n done."

that whole tie the lever to the handlebar thing is a legend, and is of no particular use.
But what do I know? I've only R&R'd 30 -or 40 front brakes.
I'll go hide now.
It is a thing for OLD brake lines to become so soft and or start shedding rubber bits internally, as to be completely useless/dangerous.

Thanks Gary! You're correct, I didn't do the complete procedure. Certainly didn't get a flow back to the MC. I'm still suspecting the 'Joint.' I'll give it a go after I get the new brake lines.

 

[joebgd]

I just read another Gary post about front brakes I think I did it right w the exit banjo below reservoir. I never took the piston out tho. I was changing to as lines. Is that right Gary? Exit port lower than reseviour.

 

[Mikey]

This looks like the thread I need !!
https://www.xs650.com/threads/rebuild-front-brake-need-to-bleed-it-nope.58245/
Edit : and I had the thread bookmarked, I guess next time I'll check my bookmarks too

 

[gggGary]

"slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line"

When you put on the line as above do you fill the line too from the top end ?
And do you have the slave cylinder mounted on the bike ?

I'll flesh it out some more.
Caliper off the carrier.

Be sure this has been removed cleaned greased, very important right @Kevin Werner ?

Off the fork, piston pushed in JUST past the sealing ring, fill completely from the port where the hose will attach, then attach the hose, with washers tighten the banjo bolt. Keep the caliper off the fork.

You might be able to push in the piston with your fingers or use a C-clamp. Turn the c-clamp handle in slowly, the fluid can really squirt out of the port into the reservoir, and all over the bike! unscrew the c-clamp a few turns, the brake lever should easily pump the piston out against the clamp. You can push t he piston back with the c-clamp and pump it out a couple times before reinstalling the caliper to be absolutely positive no air remains trapped. As a test the brake lever should be able to exert a lot of force on the piston against the c-clamp, you'll be able to see the clamp flex!
Edit more pics!
MC tilted so any trapped air will exit into reservoir.

Compensation port is hidden by (anti squirt) tab on reservoir extension.

 

[gggGary]

I just read another Gary post about front brakes I think I did it right w the exit banjo below reservoir. I never took the piston out tho. I was changing to as lines. Is that right Gary? Exit port lower than reseviour.

Uphill from caliper piston, port, hose to MC (turn bars full left, bike on side stand) what ever it takes so the MC is angled downhill towards where the line attaches. It doesn't hurt to set bike this way and squeeze release the lever a few times after an hour or so, repeat now and then it will get any sneaky air bubbles that may be hanging out right at the MC out through the reservoir..

 

[Mikey]

So what your saying is that the slave cylinder once filled and line connected to MC and slave cylinder has enough brake fluid to fill the line from bottom to top
I wouldn't think there was enough volume
I guess looking at my 75 that last little solid line that connects to the slave cylinder is pretty small

 

[Vincenthdfan]

Vincent,

Thanks for your comments. What's your idea of cheap? I see one on Harbor Freight website for $100. Not exactly my idea of cheap but I'm a tightwad. There are cheaper ones but they're hand operated.

My original hoses seem OK but I don't know how to tell for sure. Any ideas on that? I suppose that could be my problem. I just can't figure why I can't force fluid through with both ends open. I've been suspecting the little midway box but I really don't know.

Not having a problem with pressure building too much. I'm not getting enough.

Question: I only see the 1 hole in the MC. Can you say where the small one is in relation to the bigger, visible one? I'll look closer & maybe I'll see it.

This is the one I have been using for years $32.99:

Remove that useless nipple fitting on the hose of the tool and just stretch the tools rubber hose over the bleed nipple on your caliper.

As far as testing the hoses...put your finger over the back side of the banjo and blow through it with your mouth...feel the other banjo end...there will be next to zero air coming through. Then compare with a known new/good hose...no comparison in air flow, trust me on this.

The junction can get clogged with gunk too, but a quick spritz of brake cleaner will rinse it fine.

https://www.harborfreight.com/brake-fluid-bleeder-92924.html

 

[gggGary]

So what your saying is that the slave cylinder once filled and line connected to MC and slave cylinder has enough brake fluid to fill the line from bottom to top
I wouldn't think there was enough volume
I guess looking at my 75 that last little solid line that connects to the slave cylinder is pretty small

Yes this procedure is not so easy on the early caliper, you can't retract the pistons with a c-clamp like you can on the late caliper.

 

[gggGary]

See my post above for more pics and splain'n

 

[gggGary]

So what your saying is that the slave cylinder once filled and line connected to MC and slave cylinder has enough brake fluid to fill the line from bottom to top
I wouldn't think there was enough volume
I guess looking at my 75 that last little solid line that connects to the slave cylinder is pretty small

Yes that piston has a large diameter, plenty of fluid to start to fill the reservoir.