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Technical 51 merc carb choke help

Discussion in 'Traditional Customs' started by solo_909, Mar 26, 2019.

  1. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
    Member

    Carb choke question,


    I have a 51 Mercury with the auto choke carb. It’s the original carb which has the oil bath that attaches in the side.


    I recently screwed up the choke adjustment after a rebuild ( I know I’m stupid ) anyways so I’m trying to get it back to where it was. Here’s what I’ve done.


    On a cold motor I disconnected the throttle linkage. I then turned the choke counter clockwise to open the choke plate a little. Once I did that I held the throttle down about quarter throttle and then turned the choke back clockwise until it closed gently and then I tightened it down. Is that correct?


    My question is does the choke linkage ( see photo ) on the left side that the idle screw touches need to be in a certain position when doing this?


    Second question should the throttle linkage be installed a certain way? Meaning if it’s too short it would keep the throttle open and if it’s too long would it stop the choke plate from opening? What’s the right way to attach the throttle linkage to the pedal lever?


    Thanks in advanced.




    E932DA5A-2EDF-4341-9976-DA9AE52471D4.jpeg EAC85E19-EF0A-43D2-9DEE-B06F8FB09AE2.jpeg
     
  2. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
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  3. saltflats
    Joined: Aug 14, 2007
    Posts: 9,967

    saltflats
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    from Missouri

    Does your choke stat have any markings on it?
    Most will have small marks with one in the middle being the standard setting, then you adjust one or two mark as needed for your climate.
     
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  4. BJR
    Joined: Mar 11, 2005
    Posts: 6,295

    BJR
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    Got a picture of the other side of the carb?
     
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  5. solo_909
    Joined: Apr 9, 2006
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    solo_909
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    Yes it has the choke markings on it however that’s where I messed up I untwisted it so not I’m not sure if the tension is correct.

    I’m trying to figure out how to initially set up the choke before fine tuning it.
     
  6. saltflats
    Joined: Aug 14, 2007
    Posts: 9,967

    saltflats
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    from Missouri

    Try it on the middle mark and see how it does.
    If on the middle mark and the choke closes then you should be close.
     
  7. carbking
    Joined: Dec 20, 2008
    Posts: 2,753

    carbking
    Member

    Do NOT disconnect the choke linkage.

    When the ambient temperature is between 65 degrees F. and 70 degrees. and a cold engine (sat overnight):

    Remove air cleaner
    Loosen choke cover retaining screws
    With one hand, rotate the throttle fully closed, then release, then rotate to approximately 1/2 throttle and hold
    With your other hand, rotate the choke cover until it falls open, then reverse until it TOUCHES closed, no tension
    With your third hand, snug the cover retaining screws.
    Replace air cleaner

    Go play!

    Jon.
     
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  8. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
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    Thanks!

    When you say rotate the throttle close what exactly are you saying? How do I rotate the throttle?
     
  9. BJR
    Joined: Mar 11, 2005
    Posts: 6,295

    BJR
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    I think he meant open to set the choke, not closed.
     
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  10. carbking
    Joined: Dec 20, 2008
    Posts: 2,753

    carbking
    Member

    Rotate the throttle arm on the carburetor to wide-open which releases the lockout from choke to fast idle cam, and allows the choke butterfly to be set.

    Same as pushing the footfeed to the floor and then releasing, but doing it under the hood where you are working.

    Jon.
     
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  11. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
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    A little update, I made the proper adjustments as the directions above but I think I’m still having issues as I have stumbling when driving and pressing on the gas. It seems to clear if I kind of run it hard though. Any idea what may be causing that?

    Also when I did the first step of the carb adjustment “pressing the gas peddle to the floor” the idle screw never came off the high carb step. It seems to just stay on the high step no matter of the carb is cold or warm.

    The carb was rebuilt before installing in the car so do I need to adjust something else?

    Thanks!


    D1693FA4-5C2A-477E-91AA-649A7951C326.jpeg
     
  12. saltflats
    Joined: Aug 14, 2007
    Posts: 9,967

    saltflats
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    from Missouri

    So does the choke open up when the engine gets warm?
     
  13. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
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    Not really sure, I’ll have to check that tomorrow.
     
  14. carbking
    Joined: Dec 20, 2008
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    carbking
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    This would have been my next question.

    Jon.
     
  15. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
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    Okay so I warmed up the car this morning and the choke plate does open slightly but...... when pressing on the throttle the choke step linkage never moves so when pressing on the throttle the idle doesn’t drop down. It also seems to run really rich with the jets only open 1/4 turn out 9039E3DC-2A1D-4C89-9C9A-71F9341FA603.jpeg 3ED83FD0-8577-4D71-9CAA-0E2E5B8C6EAD.jpeg
     
  16. carbking
    Joined: Dec 20, 2008
    Posts: 2,753

    carbking
    Member

    Did you check for vacuum on the choke housing, and the absence of pressure on the choke tube as we discussed?

    Jon.
     
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  17. saltflats
    Joined: Aug 14, 2007
    Posts: 9,967

    saltflats
    Member
    from Missouri

    I am guessing there is a small metal tube going to the choke stat, if so see if it is getting hot when the engine is running.
     
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  18. solo_909
    Joined: Apr 9, 2006
    Posts: 1,764

    solo_909
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    So I’m sending the carb back to the guy who rebuilt it.

    I pulled the heat tube out and it seems clean and clear with no carbon build up so it wasn’t that.

    Something just isn’t right with it. I set it maybe like 3 different times however the stumble wouldn’t go away. Plus once the car was warmed up when I would press on the gas pedal the idle would get higher not lower. Plus when trying to adjust the choke plate with the black knob i has to turn it clock wise to shut the plate which is the opposite of lean.
     
    Last edited: Mar 30, 2019

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