Thread: carb rebuild for leaking dashpot

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  1. #1 carb rebuild for leaking dashpot 
    Little Brit
    Join Date
    Feb 2012
    Location
    Wallingford,CT
    Posts
    18
    One of my twin strombergs (1980 4 cyl 5 speed) doesn't hold dashpot oil for very long. When low, the engine stumbles under load over 2k rpm. Carbs have always been fine, I never touched them, (they weren't broke so I didn't fix them). Well now its time. I am thinking of getting a carb rebuild kit. Is there a way to just address the dashpot issue, or do I need to go through the whole rebuild? I know it could use it, I just do not want to reassemble them and have issues. they look fairly simple, I have the Triumph manuals, so maybe I shouldn't be to concerned?

    Anybody have any tips before I dive in? Thanks in advance for any advice.
    1980 TR7 5 Speed
    2000 BMW Z3
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  2. #2  
    Spitfire
    Join Date
    Jan 2014
    Location
    Portland, OR USA
    Posts
    1
    Tom:

    Yes, you can just repair the leaking dashpot oil. There is a small o-ring in the mixture adjuster. It is a standard size, and a neoprene or Viton o-ring from the hardware store will fix it very nicely for just a few pennies.

    Remove the air valve and diaphragm from the offending carb. Remove the grub screw that holds the needle assembly in the air valve, and use the mixture adjusting tool to rotate the mixture setting counter clockwise several turns until you are certain that the needle is free of the adjuster and is no longer held in place. GENTLY pull on the needle to remove it and the needle carrier from the air valve. Using a piece of welding rod or other stiff wire, from the bottom of the air valve push the adjuster up and out of the top of the air valve. It will be stiff, so don't be afraid to put some pressure on it.

    When the adjuster pops out from the top of the air valve, you will see that there is a small o-ring on it, this is what you need to replace. Take it with you to the hardware store and go through the SAE o-ring bins until you find the right size. It is an off the shelf size, so you will not have any problems. It will cost you a whopping $0.49 for the o-ring, so you might as well get two and replace them in both carbs.

    As they say, assembly is the reverse of disassembly.

    Cheers,

    Darth
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  3. #3  
    Little Brit
    Join Date
    Feb 2012
    Location
    Wallingford,CT
    Posts
    18
    Thanks, Darth,
    Your advice is just what I am looking for. Now I know exactly where to look for the issue.

    I am going to buy the adjustor tool and just in case a carb rebuild kit though the Wedge store,(if the diaphragm looks sketchy when I remove.) I will post my results when I do the repair, (might be a little while as its quite cold up here lately). I appreciate the quick reply, as always this forum is a great source of info and tips.

    Thanks again,
    Tom
    1980 TR7 5 Speed
    2000 BMW Z3
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  4. #4  
    Ole Boy
    Join Date
    Feb 2012
    Location
    Ottawa, Ontario, Canada
    Posts
    410
    Change the diaphragm if you have no idea of its age! Suggest you do both, since some replacements use rubber of different thickness or flexibility. You can carefully examine them, and usually they start to crack with age where they wrinkle/fold as the piston/air valve moves up and down.

    David
    1979 Triumph TR8 Coupe
    1981 Triumph TR8 Convertible
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  5. #5  
    Little Brit
    Join Date
    Feb 2012
    Location
    Wallingford,CT
    Posts
    18
    Good Advice, I was thinking that to keep them matched. I am the second owner (24 years), and I knew the original owner. These carbs have never been opened, so I am sure they are due! I will give the carbs a good a cleaning while I replace the diaphragms but I am hesitant to dig deeper than the dashpot repair. I'll take it one step at a time.

    Thanks again,
    Tom
    1980 TR7 5 Speed
    2000 BMW Z3
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  6. #6  
    Little Brit
    Join Date
    Feb 2012
    Location
    Wallingford,CT
    Posts
    18
    Repaired leaking dashpot, followed your posts and found a nice link on internet. Replaced rubber washers and diaphragms on both. I measured how far the metering pins were sticking out and put them back at same position. ( Both carbs were the same length.) Fired right up and runs great. The new diaphragms seem to have a softer more flexible rubber than the used ones so that is helping with response. Also bought some parts from WedgeShop, and replaced my rubber brake lines. She is good to go!
    1980 TR7 5 Speed
    2000 BMW Z3
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  7. #7  
    Glad you got it up and running!
    The Wedge Shop
    Fast.British.Reliable.
    www.thewedgeshop.com
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