Front brake rebuilt: filling back the system

I'm finished with the front brake rebuilt: put new seals in the calipers, new SS brake lines, rebuilt the MC and put all the parts back on the bike.

Now it'S time to fill the system with new brake fluid and bleed the lines. It was a long time ago when I did that the last time, and I find the manual is not very helpful with how to fill the lines back.

My question is: do I simply fill the MC reservoir, let it opened, strap the brake lever to the handle, open one bleeder (or both) and let is work its way down itself for several hours, filling the reservoir when needed, or do I pump it down thousands of times?

EDIT: there might be something wrong with my MC, when I pump the lever with the MC banjo opened, there is no fluid coming out...

 

Pumping's the way. If nothing coming out then yes clearly something is amiss at the m/c end.

 

it takes awhile to get it to pump when starting fresh. fill the MC. Cover it. Put teflon tape on the bleed screw threads. Close both bleed screws. Try pumping. Check/fill MC fluid. Repeat. Repeat. Now after pumping, try to crack one of the bleeds while holding the brake on. Then retighten bleed screw. Repeat repeat repeat. It's a slow process. I got frustrated the first time.

 

I already had Teflon on the bleeder screws. I'll try your method and report progress (if any).

 

Am I right or wrong assuming that some fluid should spit or jerk pretty hard out of the MC banjo bolt if cracked open while pumping the brake lever? I don't get anything but one of the crush washers moving slightly...and I can have the MC to build any pressure at all.

Before anybody asks , both holes in the botttom of ther reservoir are clean.

 

UPDATE:

I decided to go to my parts bike storage and pulled its MC off to try to bleed the system with it. The funny part is that even if I have two Seca900 of the same year, the MCs are a bit different. One as the sight glass in front and the other in the back, and the brake switch isn't of the same model either.

But the important thing is that the MC parts bike fits on my other Seca. So I started pumping the juice down with it and it seems to work, at least I have some fluid and bubbles coming out when I open a bleeder.

I have pumped and bleeded for more than 1 1/2 hour and still don't have a good lever.

MY QUESTION: for overnight bleeding, do I strap the lever to the handle with a rubber band and leave the MC reservoir open to allow bubbles to come out thru the reservoir? Other suggestions?

 

Get a rebuild kit for your master cylinder. Unless you know that it has been rebuilt within the last five years (as in YOU rebuilt it) there is no guarantee that it will build pressure. (you rebuilt the calipers already, didn't' you? (didn't you!?).

As to your question: Yes, but there is a faster way. Clamp the lever, then use a vibratory sander (without any paper on the pad) to work the bubbles up from each caliper, and into the master cylinder. Two slow passes on the whole system usually does the trick. You may want to re-bleed the system following your first ride.

 

k-moe

Thanks for the trick, now that you wrote it, I remember I read it before in one of your posts.

The MC from the parts bike (the Yellow Seca) is just a temporary solution because my recently rebuilt MC (from my Red Seca) was apparently unable to build any pressure.

AS for what I exactly did to my front brake system, I mentioned it at the very beginning of this post:

"I'm finished with the front brake rebuilt: put new seals in the calipers, new SS brake lines, rebuilt the MC and put all the parts back on the bike."

I'd add that I put new crush washers but I cleaned the old banjo bolts and reused them.

EDIT: WHen I bought the Yellow one, the MC did work properly when I had to stop the bike while pushing it, for example.

 

The banjo bolts should be fine, if they were degraded to the point that they would have caused a mechanical problem any sane person wouldn't have considered using them.
Whenever I rebuild a brake system I fill the calipers with new fluid, too. If for no other reason than to save myself some handle pumping later, but I have never had one not come up to pressure fairly quickly, maybe a dozen or so squeezes.

 

I just disassemblied the Red Seca MC I rebuilt to see if I messed with something but evrething seems to be at the right place



So I tend to think that I was a bit too enthusisastic when I cleaned the bore of the MC with the wood-peg and sandpaper method...but I used 800 and 1500 grit, it chouldn't have removed to much material.

WHat do you think?

 

try bench bleeding the mc. fill the res. and put your finger over the hole where the banjo bolt goes. then pump the brake lever to see if it builds pressure and expels the air. then put it all together and try again. I would put blocks of wood between the pads in the calipers and raise them above the mc for bleeding, but that's just me.

CN

 

Sounds like a good plan for the MC, I'll give it a try tomorrow morning. Thank you!

 

I don't have lots of tools but I really like this one:



It makes it so much easier to remove and to put back in the da** C-clip holding the MC piston in place. It is just a matter of seconds!

 

Well, I have bad and good news.

THe good news is that I finally got a good lever. WHen I decided to bleed at every banjo bolt, I got plenty of bubbles from one of calipers and from the MC banjo, and then the lever felt stiffer almost immediately.

The bad news: there is definitely something wrong with the MC I rebuilt, I have a slow leak from the bore, not a good thing when you try to build pressure. One of two things: the kit I got from Len is defective or I sanded the bore too much when I cleaned it (possible, but I doubt it).

Other bad news is that with the spare MC I built good pressure with, I messed up with one of the cover bolts: the head of the bolt broke off, I drilled the stem and used an extractor, it broke in the stem of the bolt...I can put the cover with just one bolt but it will not be a viable long-term solution.

What are your suggestions?