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Discussion Starter · #1 ·
Today I will be rebuilding my front calipers and adding steel braided lines. Thereafter, I will obviously have to bleed the front brake system from dry. I know this subject has been well-documented on the site. But I have not seen any lately, so I'll share my experience.

Shoutout to Mad8v for providing me with two used calipers. When I was reinstalling one of my pistons, it got stuck. Then I buggered it up removing it. A new piston was around 30 bucks. Pistons rarely go bad (unless an all-thumbs old fart bangs them up). So used would be fine. Mad8v sold me two calipers with all pistons for less than the price of a single piston.

My understanding is that bleeding the front system is a pain in the ass, if not simply tedious and laborious. So I researched for some tips. Again, here's Mad8v:



And here's an interesting find on bench-bleeding the master cylinder:


I'll check in later today with my success/failure.
 
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I don't know why people make a big deal about bleeding the front brakes :/


I've never had trouble bleeding front brakes on any Motorcycle and never had to use anything but a jar with a bit of brake fluid in it and a bit of 6mm ID pipe it as a one-way valve. The only time this changes is if the M/C or Caliper/Bleed nipple is faulty.

If I need to prime the M/C because it's been emptied or let to drop low I just fill it up with one of the bleed nipples open,spit on my hand and place it on top of the M/C to create a seal/partial vacuum and then pump the lever until the fluid flows and top-up as required then proceed to bleed as normal.

I always bleed the longest side first e.g left hand side,then the right and then repeat a 2nd time to make sure all air is out. I refreshed my front Brake fluid a couple of weeks ago and even lazily it only took less than 30 mins :)

PS

Small 8mm metric spanner/wrench required and a JIS Screwdriver for the M/C screws.
 

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Another technique that may assist. Make sure that the two little holes in the bottom of the master cylinder are clear. Position the bars so that the master cylinder is at its highest point.

With all the slave cylinder bleeders closed, squeeze gently on the brake lever, you should see some bubbles rise out of the master cylinder bleeder holes. Allow the lever to snap back.

Repeat until you see no more bubbles or your hand gets sore.

This is what happens to air bubbles generated in everyday use in the vertical lines. They rise to the top and get squirted out when the brake lever is applied. The bottom bleeders are only there to release pesky bubbles trapped in the slave cylinders. And of course to allow flushing out old brake fluid with new.
 

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What does this mean? Please clarify.
Just attach a piece of Tubing to the bleed nipple 6mm/ 1/4" ID ( Internal Diameter) and long enough to put into a jar on the ground with a couple of inches of old or new brake fluid in it.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=1/4"+fuel+line&_sacat=0




When you pump the fluid though you will see air bubbles come up through the fluid which prevents it going back into the system :)

On cars I used to use something like this which if I had one could use one the bike/s,

one-way brake bleed valve: Search Result | eBay"+fuel+line&_osacat=0



HTH :)
 

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I'll usually reverse bleed a dry system with a 100mL syringe from the bottom up. Push the pistons all the way in, then I'll leave the banjo at the master slightly loose and wrapped in towels so I can push fluid up to that point. If it's a 2-line system, loosen the bleeder on one caliper and connect the filled syringe with a zip tied end (better connection) and fill until it starts dripping a bit up top. Then do the other side. After both primed to the top, then I'll just bleed the rest conventionally. I usually expect to do the full bleeding over two days. It'll work well enough right away, but I always get a few bubbles to come out when I try it again after moving it around and then letting it rest for a day.
 

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... With all the slave cylinder bleeders closed, squeeze gently on the brake lever, you should see some bubbles rise out of the master cylinder bleeder holes. Repeat until you see no more bubbles.
+1

This is an excellent trick not a lot of folks know about. As George said, "squeeze gently" like 1/4 lever travel.
 

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Discussion Starter · #8 · (Edited)
Make sure that the two little holes in the bottom of the master cylinder are clear.
Which two little holes? Inside the reservoir?

With all the slave cylinder bleeders closed, squeeze gently on the brake lever, you should see some bubbles rise out of the master cylinder bleeder holes. Allow the lever to snap back.
Simply (gently) pump on the lever and that will bleed the brakes? On a dry system?

Tee? What's the process/secret?
 

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Tee? What's the process/secret?
What George is talking about with the short lever pulls is "burping" the master cylinder. If air is trapped at the MC or at the top of the line, "burping" will usually get it out.

Take a look at the second video you posted @1min20sec. This is exactly what you will see when looking into the reservoir. Keep doing short lever pulls until no more little bubbles come up. Tapping the line with a screwdriver while doing this will help move the standing bubble if it is stuck.

Another method to get air out of the MC and top line is to crack the MC banjo bolt, as Mad8 showed in his video. This works well but is a little messy.

The syringe method to push fluid up from the bottom or the vacuum method to quickly pull fluid down from the top can get around the problem too.

Once the air is out of the top of the system, you still need to do the normal method to bleed the lower lines and calipers.

Usually, it is the standing air at the top of the system that gives folks trouble. If you have a standing air bubble, you can pump a gallon of fluid through the system and still have no lever.

Generally, standing air bubbles are only a problem when changing lines. If just flushing fluid, the normal squeeze/open/close/release method should work fine, and none of the above "tricks" are necessary.
 

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Discussion Starter · #11 ·
Thanks Tee, that's what I thought, and my experience here proved it. To get most of the air out I used the old fashioned method of pump, pull, loosen valve, tighten valve, repeat. I got most of the air out, and am getting some lever.

After filling the lines, I replaced the bleed valves with SpeedBleeders, and that was a smashing success. Those things really work. And to boot, the shank on the end of the valve is much longer than the standard bleeder, which helps to keep the drain hose tie-wrapped to the valve.

It was interesting, while I was pumping, I noticed the tiny bubbles being released in the reservoir, as Tee and George pointed out. I've never noticed this before. As it stands, all's well that ends well.

As a last point, I noticed a little stickiness in my front brake lever about half way through it's motion. Sounds like I also need to rebuild my master cylinder. That will be next weekend's project.
 
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Discussion Starter · #12 ·
I got a Mity Vac years ago. Have bled many brake systems on bikes, cars, trucks with it. Even used it for testing some emissions stuff on a couple cars I've had. Been a well spent $30..
The issue I had with the Mity Vac when I rebuilt my rear caliper earlier this year was I had a hard time keeping the hose on the bleeder valve. I even tried zip-tieing it on, but it still would not stay on. I think maybe I was plumping it up too much.
 

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The issue I had with the Mity Vac when I rebuilt my rear caliper earlier this year was I had a hard time keeping the hose on the bleeder valve. I even tried zip-tieing it on, but it still would not stay on. I think maybe I was plumping it up too much.
There's one of the little pop on right angle adapter things that fits over the bleeder valves pretty tight. I pull a vacuum on it, then hold my thumb on it to make sure it doesn't come off when I crack the bleeder valve.
 

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Discussion Starter · #14 ·
There's one of the little pop on right angle adapter things that fits over the bleeder valves pretty tight. I pull a vacuum on it, then hold my thumb on it to make sure it doesn't come off when I crack the bleeder valve.
Yea, I should have bought one of those. I saw the same in Mad8v's video.
 

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Discussion Starter · #16 ·
After doing the above ( excellent advice) lock the brake lever in the on position over night. I found this has made a noticeable difference in helping to remove trapped air, did for my rear brake.
I'm going to try this tonight. Revisiting my front brakes now, my lever is not nearly as sensitive as it was before I rebuilt the calipers and added the steel brake lines. The lever goes almost to the grip, whereas, before I did the work, the brakes were quite touchy, requiring much less lever travel. They are much stronger now, but far too much lever travel.

I can only assume it's because I still have air in the lines. Here's what I did.
  1. Filled the lines using the pump, hold, open, close, repeat method. I did this on each caliper until I could see no more bubbles.
  2. Went to the MC and did the gentle pump, followed by rapid release of the lever, as suggested by Tee and George. I did this until I saw no more bubbles.
  3. Replaced the bleed valves with SpeedBleeders, then bleed some more just for good measure.
  4. Tiewrapped the brake handle lever in the brake position for about two hours, as Soulspinner suggested. Tonight I will do this all night.
  5. Still long travel on handle, so I bleed it at the MC using the double banjo, and Mad8v suggested.
I ordered a MC rebuild kit because the lever feels a bit sticky. But it has been this way since I've owned the bike. Like I said earlier, the lever has a lot more travel now than it did before I did all of this stuff, so I obviously screwed something up. There's got to be air is the system.

Ideas, suggestions?

Thanks,
-Geo
 

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I'm going to try this tonight. Revisiting my front brakes now, my lever is not nearly as sensitive as it was before I rebuilt the calipers and added the steel brake lines. The lever goes almost to the grip, whereas, before I did the work, the brakes were quite touchy, requiring much less lever travel. They are much stronger now, but far too much lever travel.

I can only assume it's because I still have air in the lines. Here's what I did.

Thanks,
-Geo
Tying the brake lever and leaving overnight can help.

Important!. I've realized I've left out a very important part of my Old-School procedure as I just took it for granted. When I see there's no more bubbles in the fluid I'm down at the bleed nipple and with my hand on the brake lever held in I tighten the BN so no air can creep into the threads and into the system.
 
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Discussion Starter · #18 ·
Okay, this is starting to piss me off. In review, I did the following:
  1. Rebuilt the front calipers with BrakeCrafters kits.
  2. Installed Galfer stainless lines (the ones with the double banjo at the master cylinder).
  3. Rebuilt the master cylinder with a BrakeCrafters kit.
  4. Bleed the lines the old-fashioned way (pump, hold, open, close), starting with the left caliper, then to the right, then at top at the double banjo.
  5. Installed SpeedBleeders at the calipers and performed final bleed.
  6. Used George Young's suggestion of pulling the lever, then letting go, which produced tiny bubbles for about 20 minutes.
  7. Ziptied the lever to the grip and left it overnight.
The result...still too much lever travel. I must have air in the system, but I went back and bleed again, still the same. The thing I don't understand is I have much more lever travel now than before I started doing anything with the front brakes. I rebuilt everything because the pistons were sticking.

Here's my question. Is it possible I nicked a caliper seal when reinstalling a piston, which may let air in? If this is the case, it would seem it would leak brake fluid. But I don't see any leeks. Any suggestions from the SVR Braintrust?

One other thing, the calipers were pretty gunked up. I scraped and brushed them, then ran them through the untrasonic cleaner. Thereafter, I let them dry overnight, then I blew them out with a compressor. But, the first time I installed one of the pistons, I could not get it passed the seals, even trying to jam it in. So I took it apart again, but the piston did not want to come out. Ultimately, I sacrificed the piston to get it out. I replaced the piston (thanks Mad8v), and re-used the seals because they were new. But, I could have buggered it up with the piston episode. Again, have any of you experienced air leaking passed caliper seals?

Thanks guys
-Geo
 
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