Bleed

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Pridanc
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Joined: Thu Feb 13, 2020 9:39 pm
Location: Austin, TX
Location: Austin, TX

Bleed

Post by Pridanc »

Folks, gosh knows this has been hashed one-million and one times but I'm flummoxed as I've never had an issue bleeding motorcycle brakes.

The skinny: I just got done rebuilding both MC's and all three calipers as well as replacing each brake line. Of course the rear took 2 seconds to bleed out and all is perfect.

I've had "fun" bleeding fronts before but here is my issue and my thoughts or just me expressing confusion, not fact except for what is happening.

Both calipers bleed clean fluid. No air, nada. However the brake lever pulls back to within 5mm of the Handle bar before any semblance of brake pressure arrives which is clearly too late to do anything much less permit increase pressure.

The catch is this as I see it: RT FrT caliper does it's job of taking up the slack to engage itself (as you'd expect after a rebuild and the pistons being pushed into the bore prior to reassembly) as the lever is pulled. All good but when I release the lever the caliper goes back to where it was. Um...WHAT? I understood that the MC should recover and refill / reload itself before the caliper could so that the caliper would, up to a point, start closer to it's useful position.

Is it possible that the check valve on the piston in the front Master Cylinder is not working or some such?
Help please. I'm going nuts and partly because I've never encountered any issues with motorcycle brakes in my life. I guess it is my comeuppance right?
Thanks in advance as I'm about ready to take my dull chainsaw to it. Grrrrrr

daves79x
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Re: Bleed

Post by daves79x »

You likely still have some air, which taping the lever slightly pulled for a few days will cure. I have seen what you are describing though. Try this: remove the caliper and pump the piston out farther than it is now. Then carefully push the piston/pad in so there is JUST enough clearance to slip over the rotor. See if it now does not relax so far. Repeat if necessary.

Dave

AshishNJ
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Re: Bleed

Post by AshishNJ »

Can you try blender pump at calipers ?

Pridanc
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Joined: Thu Feb 13, 2020 9:39 pm
Location: Austin, TX
Location: Austin, TX

Re: Bleed

Post by Pridanc »

Gents, can't thank y'all enough as I do believe the issue has been fixed. I bled the system again using both a vacuum and the pump, pressure, release, pump again methods. Result was good clean airless fluid as before. Good stuff. However, If I had to pick one thing that got me over the hump, I'd point to the suggestion to pull the caliper, stroke the lever to push the piston out so that pads/piston were about where they'd live normally, reinstall caliper and work lever again. Voila, normal function is back.
A million thanks to each of you. I am grateful.

daves79x
ICOA Technical Director
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Posts: 3894
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA
Location: Knox, PA

Re: Bleed

Post by daves79x »

Just doin' our job here. Glad it all worked out.

Dave

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