Author Topic: Bad out the box master cyl for convert?  (Read 2502 times)

Offline gearman

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Bad out the box master cyl for convert?
« on: April 22, 2018, 12:50:10 PM »
I bought a new brembo knockoff mc from a well known Guzzi  seller and have spent hours trying to bleed the air out. I used a vacuum bleeder, a reverse bleed, and the old pump and hold. I even loosened the front brake light switch and rotated it thinking an air bubble might be stuck in it.Nothing works.There is no air bubbles in my bleeder hoses. I called the seller last week and left a message asking if they had ever had bad out the box mc's. He never called back. when I first got the mc there were some small metal chips in the reservoir,which I cleaned out. Also the bore for the clamp was 5 thou. undersize and I had to hone it to get it on the bar.How can I test the mc to see if it is any good. I am  puzzled.

oldbike54

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Re: Bad out the box master cyl for convert?
« Reply #1 on: April 22, 2018, 12:57:22 PM »
 You are testing it , it is bad .

 Dusty

Offline gearman

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Re: Bad out the box master cyl for convert?
« Reply #2 on: April 22, 2018, 01:27:26 PM »
Have you ever gotten one bad?

oldbike54

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Re: Bad out the box master cyl for convert?
« Reply #3 on: April 22, 2018, 01:29:42 PM »
Have you ever gotten one bad?

 Yes . The metal chips are a clue , the work was sloppy . Sending a PM .

 Dusty

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Re: Bad out the box master cyl for convert?
« Reply #3 on: April 22, 2018, 01:29:42 PM »

Online RinkRat II

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Re: Bad out the box master cyl for convert?
« Reply #4 on: April 22, 2018, 02:40:25 PM »
Hey Gearman,  Are you sure the piston is returning all the way back to the rest position to pick up more fluid?  My $.02 :evil:

     Paul B  :boozing:
A Miller in the hand is worth two in the fridge.

Offline gearman

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Re: Bad out the box master cyl for convert?
« Reply #5 on: April 22, 2018, 03:10:55 PM »
Hey Gearman,  Are you sure the piston is returning all the way back to the rest position to pick up more fluid?  My $.02 :evil:

     Paul B  :boozing:
I think so. I get a geyser in the reservoir.

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Re: Bad out the box master cyl for convert?
« Reply #6 on: April 22, 2018, 03:43:33 PM »

      Almost sounds like they tore a cup on the piston and its bypassing fluid internally. Bench bleed it and see what happens.
   
         Paul B :boozing:
A Miller in the hand is worth two in the fridge.

Offline gearman

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Re: Bad out the box master cyl for convert?
« Reply #7 on: April 23, 2018, 10:31:30 AM »
Well i bench tested it and it pushes the air out to a point but it is like the check valve or whatever does not work.The pictures shows that the clear column won't go all the way to the reservoir.  Also when I unscrewed the cap this time the whole reservoir assy came off too. Made a mess. Ideas?




oldbike54

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Re: Bad out the box master cyl for convert?
« Reply #8 on: April 23, 2018, 10:41:54 AM »
 Ideas ? Yeah , it's a piece of junk , don't waste anymore time on it .

 Dusty

Offline John Croucher

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Re: Bad out the box master cyl for convert?
« Reply #9 on: April 23, 2018, 10:49:27 AM »
Is it possible you have a smaller piston size than the previous m.c.?  This will cause the lever to fill mushy and like it never pumps up due to the low amount of fluid being pushed.  And too large a piston will give you a very solid feel and no brakes. 

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Re: Bad out the box master cyl for convert?
« Reply #10 on: April 23, 2018, 11:00:27 AM »

   No check valve, One piston, two seals one spring. Oneof the seals in backwards or torn. Sounds like Dusty sez...you got a bad one.
   
     Paul B :boozing:
A Miller in the hand is worth two in the fridge.

oldbike54

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Re: Bad out the box master cyl for convert?
« Reply #11 on: April 23, 2018, 11:23:12 AM »
   No check valve, One piston, two seals one spring. Oneof the seals in backwards or torn. Sounds like Dusty sez...you got a bad one.
   
     Paul B :boozing:

 I wasn't trying to be snarky , but recognizing facts requires calling this thing what it is . This is a brake component , not something worth taking any risk on .

 Dusty

Offline gearman

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Re: Bad out the box master cyl for convert?
« Reply #12 on: April 23, 2018, 06:10:16 PM »
Could my test be invalid because my test  hoses are too big for the volume of the mc piston?

Offline gearman

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Re: Bad out the box master cyl for convert?
« Reply #13 on: April 23, 2018, 06:27:38 PM »
bump for new question. Thank You

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Re: Bad out the box master cyl for convert?
« Reply #14 on: April 23, 2018, 06:47:52 PM »
 
   As long as there is fluid to be picked up in the reservoir that baby will pump all day long.
 
       Paul B :boozing:
A Miller in the hand is worth two in the fridge.

Offline gearman

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Re: Bad out the box master cyl for convert?
« Reply #15 on: April 24, 2018, 07:51:42 AM »
But it never gets rid of the air completely in the tube. That is why I am thinking that the volume in the tube is larger than the displacement of the mc piston. Ideas?

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Re: Bad out the box master cyl for convert?
« Reply #16 on: April 24, 2018, 08:49:41 AM »
 If it always has air while bench bleeding it's actually pulling in air from the rear seal cup on the piston. Front seal always has liquid around it.

       Paul B :boozing:



« Last Edit: April 24, 2018, 08:51:58 AM by RinkRat II »
A Miller in the hand is worth two in the fridge.

Offline mtiberio

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Re: Bad out the box master cyl for convert?
« Reply #17 on: April 24, 2018, 10:23:08 AM »
are the little holes drilled all the way through (compensation port and main port)?
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Offline mtiberio

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Re: Bad out the box master cyl for convert?
« Reply #18 on: April 24, 2018, 10:24:27 AM »
If I want to test a M/C, I mount it. Fill with fluid, and put my finger over the exit (no lines or brakes). If you squeeze lever, you should feel a push against your finger.
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Offline Two Checks

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Re: Bad out the box master cyl for convert?
« Reply #19 on: April 24, 2018, 11:02:47 AM »
bought a new brembo knockoff mc
[/size]
[/size]I think you already identified your problem.
1990 Cal III f/f  "Il Duce' III"
1987 1000 SPII "Il Duce' II"

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Re: Bad out the box master cyl for convert?
« Reply #20 on: April 24, 2018, 11:37:21 AM »

   
Quote
But it never gets rid of the air completely in the tube.
    If your referring to the bubble between your two pieces of tape, It never will beause the end is open and and the fluid will follow the inner arc of the tube and not fill the tube unless you restrict the open end or hold the tube vertical.
     
       Paul B :boozing:
A Miller in the hand is worth two in the fridge.

oldbike54

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Re: Bad out the box master cyl for convert?
« Reply #21 on: April 24, 2018, 12:27:50 PM »
 It's dead Jim .

 Dusty

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Re: Bad out the box master cyl for convert?
« Reply #22 on: April 24, 2018, 03:06:24 PM »
It's dead Jim .

 Dusty

    Just mostly dead :evil:

     Paul B :boozing:
A Miller in the hand is worth two in the fridge.

oldbike54

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Re: Bad out the box master cyl for convert?
« Reply #23 on: April 24, 2018, 03:57:30 PM »
    Just mostly dead :evil:

     Paul B :boozing:

 Semi-dead then . There should be a "no extreme measures" clause attached to this thing . It is a brake component , it might lead to a very unpleasant experience .

 Dusty

 

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