bench bleed of master cylinder..how to

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Jul 28, 2007
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3,120
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finger lakes ny
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1999 ST1100
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7959
This is what I came up with. Does this look remotely like a correct method (after filling m/c) and do you just keep pumping the brake lever until no bubbles are passing?
Then mount m/c on bike and hook up the lines? No air will enter?
And this will verify if m/c kit was properly installed?
 

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Joined
Nov 1, 2009
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387
Location
North Plainfield, NJ
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'06 ST1300A
Does this look remotely like a correct method (after filling m/c) and do you just keep pumping the brake lever until no bubbles are passing?
That looks like it'll do just fine.

The reason to 'bench bleed' a master cylinder is to purge most (if not all) the air out of the master cylinder. Thus priming the master cylinder with enough brake fluid that when you begin bleeding the brakes, you are pumping brake fluid through the brake lines, and not air. Otherwise the master cylinder can become 'air bound' and you may just end up pumping air as you try to bleed the brake system.

Then mount m/c on bike and hook up the lines? No air will enter?
Yes, air most likely will enter the brake system as you reinstall the master cylinder, but that shouldn't be a problem, as you're still going to bleed the brake system.

And this will verify if m/c kit was properly installed?
Perhaps. Of course if you installed the repair kit bits in the same way they were removed, and the master cylinder (after bleeding) behaves as you expect it to, then yes, I guess you could say the installation has been verified.
 
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