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Discussion Starter · #1 ·
Everything is flushed, fresh RBF600, tightened properly, but I keep getting air in the line unless I bleed the system every couple weeks.

Now, normally I wouldn't care too much as I never really use the rear brake, and in a panic stop, it provides some braking. But I plan to do a track day at Road Atlanta on May 5, and need to make sure that it passes tech.

I can bleed the brakes the night before, or, if the cost is reasonable, just fix the stupid thing properly and not worry about it.

I assume this this is a fairly common issue, but what is the actual fix? Replace the rear master cylinder? If so, what's the cheapest, but decent option?
 

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Everything is flushed, fresh RBF600, tightened properly, but I keep getting air in the line unless I bleed the system every couple weeks.

Now, normally I wouldn't care too much as I never really use the rear brake, and in a panic stop, it provides some braking. But I plan to do a track day at Road Atlanta on May 5, and need to make sure that it passes tech.

I can bleed the brakes the night before, or, if the cost is reasonable, just fix the stupid thing properly and not worry about it.

I assume this this is a fairly common issue, but what is the actual fix? Replace the rear master cylinder? If so, what's the cheapest, but decent option?
In for the response. Had a hard time bleeding mine also. I have removed the caliper and got it high as per the other recommendations I have got.

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Discussion Starter · #3 ·
In for the response. Had a hard time bleeding mine also. I have removed the caliper and got it high as per the other recommendations I have got.

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I guess I can try that again, get it off the bike, slip something in between the pads and then let it hang overnight in the highest position to hopefully let the bubble rise to the top. But that's what the dealer did before I bought it a few months ago and it's got air in there again.

If there is a better master to swap it out with that is a drop in unit, that's fine too...
 

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I've only ever run into this problem on my bikes that have ABS. I'm thinking it's just really hard to get all the air out of the ABS system. But at the same time, I've never had this problem with the fronts. Honestly I can't figure out how it's happening.
 

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I've only ever run into this problem on my bikes that have ABS. I'm thinking it's just really hard to get all the air out of the ABS system. But at the same time, I've never had this problem with the fronts. Honestly I can't figure out how it's happening.
I was told it had to do with the rear caliper being under.

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I think I know what you mean. Being hung under the axel. My Monster has no ABS and is underhung. It's hard to bleed without removing it but doing so and holding it higher than the master cylinder for bleeding and once that's done there's no problem. It stays air free and very solid.

But my other bikes with a high mount caliper and ABS are a pain to keep air out of them. Just like everyone complains about on the Multistrada.
 

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I think I know what you mean. Being hung under the axel. My Monster has no ABS and is underhung. It's hard to bleed without removing it but doing so and holding it higher than the master cylinder for bleeding and once that's done there's no problem. It stays air free and very solid.

But my other bikes with a high mount caliper and ABS are a pain to keep air out of them. Just like everyone complains about on the Multistrada.
I suspect the MTS has a lot to do with the heat from the cat. Recently I worked on a Hyperstrada with ABS that I suspect was difficult because of the abs pump/valving.

t_bare
 

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J

I read on the Multistrada forum some have installed bleeder banjo’s up at the abs unit. Is that possible for the Monster 1200? Would making bleeding the rear easier?
Also it is suggested the reason for the air in the lines could be heat from the motor or cat heating up the brake fluid. Thought’s?
 

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Advise to ease the pain of bleeding rear brakes

Everything is flushed, fresh RBF600, tightened properly, but I keep getting air in the line unless I bleed the system every couple weeks.

Now, normally I wouldn't care too much as I never really use the rear brake, and in a panic stop, it provides some braking. But I plan to do a track day at Road Atlanta on May 5, and need to make sure that it passes tech.

I can bleed the brakes the night before, or, if the cost is reasonable, just fix the stupid thing properly and not worry about it.

I assume this this is a fairly common issue, but what is the actual fix? Replace the rear master cylinder? If so, what's the cheapest, but decent option?

Hi,

First, perhaps your not getting all the air out of the system...just a thought as others have mentioned here.

Second; What I have done to make the whole process easier and less painful is to replace the banjo bolt on the rear master with a banjo bolt with a bleed nipple. I got mine from Berllissimoto, Lyle hooked me up with a trick titanium one :)

It worked great for me :) and no more rear caliper juggling act LOL ...it will still take much longer to bleed the rear brake. I even had to "jam" the brake pedal in the "on" position and leave it overnight to let the air bubbles rise to the top. The next day I bled a few reservoir of fluid and the pedal was hard and the brakes bled :)

Best of luck

Pete
 

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Discussion Starter · #10 ·
Hi,

First, perhaps your not getting all the air out of the system...just a thought as others have mentioned here.

Second; What I have done to make the whole process easier and less painful is to replace the banjo bolt on the rear master with a banjo bolt with a bleed nipple. I got mine from Berllissimoto, Lyle hooked me up with a trick titanium one :)

It worked great for me :) and no more rear caliper juggling act LOL ...it will still take much longer to bleed the rear brake. I even had to "jam" the brake pedal in the "on" position and leave it overnight to let the air bubbles rise to the top. The next day I bled a few reservoir of fluid and the pedal was hard and the brakes bled :)

Best of luck

Pete
Link to a bleeder for the rear caliper? That sounds so much better. I want one of those. haha
 

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Discussion Starter · #12 ·
Thanks, I will call them tomorrow. Curious how this works, as mine has a set of wires coming out of the top of mine... not sure where the bleeder would go unless it comes out the side rather than the end
 

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Thanks, I will call them tomorrow. Curious how this works, as mine has a set of wires coming out of the top of mine... not sure where the bleeder would go unless it comes out the side rather than the end
All master cylindres have a banjo bolt at the connexion point of the break line, but when you call Bellisimoto they will set you up for your bike I'm sure.

Let me know how it works out.

L8tr
Pete
 

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If you think the problem is heat from the cat, maybe you should fix the problem, not the symptom. I have a Sportster with this issue and I insulated the master from the pipe and rerouted a longer SS rear line to avoid the exhaust.
The part I’m not understanding, forgive my lack of chemistry knowledge, is please explain to me how a supposedly closed system keeps making air out of brake fluid ? In my ignorance I would assume I have a seal leak and try to fix that.
 

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Discussion Starter · #15 ·
My bike doesn't have a CAT. The prior owner had that removed when he installed the full Termi kit, and the rear brakes were bled by the dealer since that time.

The rear setup just sucks, I think is the problem.
 

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Discussion Starter · #16 ·
Talked to Bellisimoto and they said that because I have the banjo bolt pressure switch installed(because of the new rearsets), that I cannot have the bleeder valve at the master side. It's one or the other, not both.

So I will just have to bleed it the normal crappy way with the rear caliper suspended and a file or something between the pads to simulate the disc, and see if I can get any air out of there. I will flush the front and rear system entirely with a fresh bottle of RBF600 and see how it goes. If nothing else, I will wait and do it a couple days before the track day, to get passed tech, and if it slowly fades over time again I will just have to deal with it then...
 

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I've had success getting the air out of underhung calipers by doing a "reverse" flush. Use a 50ml syringe (or larger if you can find one) to inject brake fluid through your caliper, pushing it up and into the reservoir. I'd recommend flushing a bunch of fluid through the other way first to push out any crud as the orifice in the master cylinder reservoir is tiny.

As others have noted, heat can play a factor. If there is ANY air or water in your brake fluid, the high temps will expand the air and boil the water and your rear brake will either drag or feel spongy or both. Make sure the seal in the cap on the reservoir is good, and see if there's any way you can move the brake line as far from the cat/pipes as possible. I tried wrapping mine in aluminum foil which probably helped a little bit.
 

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Discussion Starter · #18 ·
I've had success getting the air out of underhung calipers by doing a "reverse" flush. Use a 50ml syringe (or larger if you can find one) to inject brake fluid through your caliper, pushing it up and into the reservoir. I'd recommend flushing a bunch of fluid through the other way first to push out any crud as the orifice in the master cylinder reservoir is tiny.

As others have noted, heat can play a factor. If there is ANY air or water in your brake fluid, the high temps will expand the air and boil the water and your rear brake will either drag or feel spongy or both. Make sure the seal in the cap on the reservoir is good, and see if there's any way you can move the brake line as far from the cat/pipes as possible. I tried wrapping mine in aluminum foil which probably helped a little bit.
I kinda like that idea... If I can find a big ass syringe and connect it to some bleeder hose, that could work. Will need a buddy to help me, as I will need someone drawing fluid out of the little reservoir as I push it through the system...

I feel like the master is far enough away with the new rearsets that he shouldn't be a problem, but you never know. I might have some adhesive backed heat shield material that I could strategically place and see if that helps. Also, the RFB600 has a higher boiling point, so that might help too...
 

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Discussion Starter · #19 ·
So today I got a couple bottles of fresh Motul RBF600 and went to town, bleeding the clutch master and slave, front brakes and then did the rear.

Front and clutch were easy, flushed everything out with fresh fluid and all bubbles are gone.

The rear was a pain. Have to remove the Termi cans to remove the rear wheel, then unbolt the caliper and flip it to the top of the rotor, to start bleeding it. I attached the bleed kit and hung it up high so it had to push the fluid up and into the can. That way the tube was always full of fluid and could not suck any air back in. I left the bleeder valve open slightly and just started pumping the pedal and fill it with new fluid. I figured pushing lots of fluid through quickly would push the air with it.

Tons of air came out. I flushed 3/4 of a bottle through it the rear to make sure there was no air in there. Tightened it all up and put it back together me went for a ride.

The rear is firm and locks up with ease now, triggering the ABS. The question of course is, how long will it last? If it makes it to my track day on the 5th that would be nice.

We shall see. There is no real heat source that I would say is too close to the rear master. Maybe it was on the oem rearsets but not these. They are up higher and away from the pipe.

Will let you know how it holds up...
 

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Discussion Starter · #20 ·
Been a couple weeks now and the rear still has plenty of pressure. Putting the caliper upside down really helped, and I think that my method did the trick.

Normally you pump up the lever/pedal, hold it, release the bleeder, let bubbles and fluid come out, tighten, pump lever up again till it is firm, repeat...

I hung a catch bottle up high and connected the hose to the bleeder valve and opened it up maybe 50%, and just kept pushing the lever over and over and filling the reservoir as it drained.

So rather than pressure, squirt a little out, then have it sit and settle for a few seconds while I pump it back up, you get more of a steady and continuous flow of fluid through the system. I think that's a better way to push bubbles through and out the ABS system...

You hang the bottle up high so that there is never any air in that hose once you start so there is no way to suck any back in when you leave the bleeder part way open...
 
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