Using a fork pump.- Mtbr.com
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  1. #1

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    Using a fork pump.

    I am trying to put air in my new SID. I pump the chamber up to the appropriate psi, and start to unscrew the pump head from the valve and all of the air escapes...what am I doing wrong?

  2. #2

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    Quote Originally Posted by ricer
    I am trying to put air in my new SID. I pump the chamber up to the appropriate psi, and start to unscrew the pump head from the valve and all of the air escapes...what am I doing wrong?
    Sounds like a cheap/incompatible pump? Or just unscrew it faster!

    I don't know the SIDs specifically, but it should be able to release the valve first, and then unscrew it while keeping a seal for a moment. You'll hear a small hiss of air escaping from the pump and valve body no matter what. Try another brand of pump - maybe your LBS can help out.

  3. #3

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    It's probably NOT the pump.

    The problem is that the valve core (little pin thingy sticking out of the air valve) needs to be tightened slightly or replaced with a shorter one. I had the same issue (not a cheap pump) on the neg chamber of my Reba, and on the main chamber of my Cloud 9, both were fixed by tightening the valve core using the proper valve core tool. You can buy valve cores and the tool at any auto parts store for very little, and its good to have them in your toolbox anyways.

    Mark

  4. #4
    jrm
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    Try...

    Quote Originally Posted by ricer
    I am trying to put air in my new SID. I pump the chamber up to the appropriate psi, and start to unscrew the pump head from the valve and all of the air escapes...what am I doing wrong?
    screwing the pump on only to the point where the pump guage registers and not screwing the pump on till it bottoms out. You might also try unscrewing the valve stem a bit so it sits further up in the valve so the pump will engage sooner...

  5. #5

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    Quote Originally Posted by jrm
    You might also try unscrewing the valve stem a bit so it sits further up in the valve so the pump will engage sooner...
    This is backwards advice. Doing this will cause even more air to escape. If the pump depresses the valve BEFORE the o-ring (or seal) of the pump seals the connection, then the air escapes. You need to make sure the pump seals before the air valve is depressed (and releases air), and this is achieved by screwing the valve core in tighter (deeper) into the valve.

  6. #6
    jrm
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    Done it on 2 forks..

    with successful results. But what i forgot to say in my OP was that i changed out the OE valve core with one with a longer plunger on it. THe valve stem tool and valve core cost less than $5..

  7. #7
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    Quote Originally Posted by MJ51
    It's probably NOT the pump.

    The problem is that the valve core (little pin thingy sticking out of the air valve) needs to be tightened slightly or replaced with a shorter one. I had the same issue (not a cheap pump) on the neg chamber of my Reba, and on the main chamber of my Cloud 9, both were fixed by tightening the valve core using the proper valve core tool. You can buy valve cores and the tool at any auto parts store for very little, and its good to have them in your toolbox anyways.

    Mark
    Yup, that's most likely it. Cheap pumps sometimes do have problems with letting air out or reading inaccurate pressures though. Either way, you're going to hear a little hissing when you unscrew it.

  8. #8
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    Quote Originally Posted by jrm
    with successful results. But what i forgot to say in my OP was that i changed out the OE valve core with one with a longer plunger on it. THe valve stem tool and valve core cost less than $5..
    where did you find the valve cores with longer stems? need to do this to my fork and shock
    "He can make even a global summit meeting seem like a kegger." M. Dowd, NY Times, 19 July 2006

  9. #9
    jrm
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    Tire store..

    Quote Originally Posted by adamantane
    where did you find the valve cores with longer stems? need to do this to my fork and shock
    Just make sure you take the original in with you so you know your getting one with a longer plunger.

  10. #10

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    Quote Originally Posted by jrm
    Just make sure you take the original in with you so you know your getting one with a longer plunger.
    I suggest that while you are there you also buy stems with 'shorter' plungers as I still maintain that longer plungers will make your problem worse.

  11. #11
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    Quote Originally Posted by jrm
    Just make sure you take the original in with you so you know your getting one with a longer plunger.
    where is "there"...are we at an automotive store or an LBS...i'm afraid on my LBS..i always manage to get some kid who never knows where things are...alot of deer in the headlights looks...i should open my own shop come to think of it
    "He can make even a global summit meeting seem like a kegger." M. Dowd, NY Times, 19 July 2006

  12. #12
    jrm
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    I go to a Big O tire store near my house

    Quote Originally Posted by adamantane
    where is "there"...are we at an automotive store or an LBS...i'm afraid on my LBS..i always manage to get some kid who never knows where things are...alot of deer in the headlights looks...i should open my own shop come to think of it
    I tried the LBS and a an auto parts store but they didnt have the selection the tire store has..

  13. #13

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    Quote Originally Posted by adamantane
    where is "there"...are we at an automotive store or an LBS...i'm afraid on my LBS..i always manage to get some kid who never knows where things are...alot of deer in the headlights looks...i should open my own shop come to think of it
    Automotive. If you get the little tool (which you need to replace the valve core), first try tightening the existing valve core first and see if that helps (It usually does for me).

    This is what you are looking for...


  14. #14
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    thanks guys...i'll start looking around and bring mine with me
    "He can make even a global summit meeting seem like a kegger." M. Dowd, NY Times, 19 July 2006

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