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Air In System After Brake Bleed... Need Some Ideas


LocalRoadKing
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I've bled my brakes on my 2010 VFR1200F with about 5 bottles for DOT4 at this point, both forward and backwards AND STILL I have excessive lever travel (to the bar at first pull) at the master cylinder. I have tilted it in many directions and have rebuilt it with new parts, I feel like I've tried everything at this point, and yet still the air in the system persists. Has anyone else been in this situation and got it successfully resolved? I'm game to try anything at this point.

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I was in a simular situation on my Valkyrie front brake rebuild.  The thing would not bleed solid....forwards, backwards whatever.

Turns out a caliper clip spring fell out of its slot, (new pads) and I was just working against its spring force......until I discovered it. (Duh!)

Now it's far better than stock.....

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Beat me to it Dude; I did the same thing on the back of my last VFR800 and had to pump the lever to get the brake working. The spring clip kept pushing the pad/piston back out.

 

Being a cheap bastard, once I get fresh clean fluid flowing during a bleed, I start to catch the bled fluid and re-use it for bleeding. 

 

I've also had success firming up a lever by tieing the lever back to the bar (or hanging a full can of paint on the pedal) and leaving it like that overnight. I don't understand the physics but this can make a slightly mushy feel go solid. 

 

I've also got a cheap vacuum brake bleeder; I've had good results winding the vacuum up and then pumping the brake to quickly blast fluid through.

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3 hours ago, Terry said:

I've also had success firming up a lever by tieing the lever back to the bar (or hanging a full can of paint on the pedal) and leaving it like that overnight. I don't understand the physics but this can make a slightly mushy feel go solid. 

I  think it works because you compress the trapped air bubbles and this makes it easier for them to migrate up the hoses to the master cylinder.

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Great news, I zip-tied my brake lever last night and I came back this morning and it's way better. It's not 100% though, but it's really close, like 90%. Definitely rideable though. I'm going to keep riding and hope the rest of the air eventually makes it's way up. I tried this trick before and had no luck, but it seems to work now after I rebuilt the master cylinder. I think the return port was partially blocked before I rebuilt it because pressure would keep building up until the brakes would lock while I tried to ride it.

 

Anyway, thanks for turning me again onto this trick, works much better when the master cylinder is working properly.

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Also highly recommend ensuring that that master is the high spot, and in this position, pulling the lever as tightly as you can and completely releasing it fully and quickly (like a flick). This can free a lot of air from the system. 

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17 hours ago, squirrelman said:

^^ you can raise the mc even higher by removing it from the bar and holding it up by the lever while tapping the line and banjo bolt. this worked for me many times.

Do exactly the same myself

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On 9/16/2022 at 1:25 PM, fink said:

Do exactly the same myself

 

so you think it's effective then and it has your enthusiastic, unequivocal endorsement , ay lad ? 

 

whats the crack ? how's the crack ?

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On 9/16/2022 at 11:58 PM, squirrelman said:

 

so you think it's effective then, and it has your enthusiastic, unequivocal endorsement , ay lad ? 

 

whats the crack ? how's the crack ?

It does what it says on the tin. I give it my wholehearted endorsement, a proceedure that also works as well when you have a hydraulic clutch to bleed and it wont go.

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