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Thread: Relaxing an overly-tight throttle return spring

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    Experienced Lancista Professorgearhead's Avatar
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    Relaxing an overly-tight throttle return spring

    I searched the forums but came up blank, so.......

    I've just rebuilt my DDHF 42 carbs on my '72 1,600, balanced them, set the mixture, and the engine now purrs beautifully, has a perfect idle, accelerates strongly, and I’m a happy guy! At low speed in 1st or 2nd gears, however, the car tends to lurch a bit, and I’m pretty sure my throttle return spring, which looks stock, is so tight that it’s essentially impossible to keep the pedal smooth. There are also the two stock (?) return springs, one on each carb. Is there a 'tried and true' way of dealing with this? Surely I can’t be the only person in the world who has this issue. Could I simply take off one or both of the carb return springs, or is that a no-no? Thank you in advance.
    Thor Frohn-Nielsen
    '72 Lancia Fulvia 1600

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    Legendary Lancista lancialulu's Avatar
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    Re: Relaxing an overly-tight throttle return spring

    Not the springs..... look at the organ pedal bearings ( old rubbery bits that dont give a smooth throttle action)

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    Re: Relaxing an overly-tight throttle return spring

    Quote Originally Posted by lancialulu View Post
    Not the springs..... look at the organ pedal bearings ( old rubbery bits that dont give a smooth throttle action)
    Thanks for that. Will check and report back.
    Thor Frohn-Nielsen
    '72 Lancia Fulvia 1600

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    Re: Relaxing an overly-tight throttle return spring

    Lancialulu: thanks for the advice. You were right. The 'bushing' at the pivot for the throttle was more of a semi-soft, grommety-thing way past it’s best-before date. I replaced it with two ball bearing races (Amcan 6900 2RS, if anyone is interested—and assuming they have the same diameter). It took a bit of fettling with the Dremel and some Emory-paper, but the result was way past expectations. Lurching gone! My throttle cable was also a bit tight, so I managed to lubricate it too. It did get me wondering if I lose any smoothness in throttle input from the cheesy way the back of the throttle pedal slides on the connecting shaft—or is that becoming way too obsessive?
    Thor Frohn-Nielsen
    '72 Lancia Fulvia 1600

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    Legendary Lancista fay66's Avatar
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    Re: Relaxing an overly-tight throttle return spring

    Hi,
    Change them for roller bearings and you'll be amazed at the difference, changed mine about 14 years ago and never had any trouble since.
    Problem is Plastic bushes that expand in the heat, besides getting sticky with age.
    Brian

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    Re: Relaxing an overly-tight throttle return spring

    Quote Originally Posted by fay66 View Post
    Hi,
    Change them for roller bearings and you'll be amazed at the difference, changed mine about 14 years ago and never had any trouble since.
    Problem is Plastic bushes that expand in the heat, besides getting sticky with age.
    Brian
    wait...... are you telling me that I should have plastic bushings on the two tangs of the pivoting throttle lever where it slides up and down against the back of the throttle pedal!? I have nothing: just the two metal tangs. Thus metal-on-metal. I’m surprised there’s enough room for a roller bearing back there, or did you do some modifications to the back of the pedal. The huge difference it made by installing the bearings on the pivot certainly makes me think that the slidey-point at the back of the pedal is a weak link in my effort to have silky-smooth throttle response.

    Thanks for the tip, Brian
    Thor Frohn-Nielsen
    '72 Lancia Fulvia 1600

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    Re: Relaxing an overly-tight throttle return spring

    Originally there were rubber "wheels" at the back of the pedal, using the two metal prongs as axle (not that were intend to rotate really). Rubber for the effect of minimising vibration transfer (silent block effect). Most of the rubber wheels have perished with age. You can put in "hard" wheels, or some put in ball bearings (but you got the get the correct size, of the will not fit snugly and allow some play, which makes for a "lose" pedal feeling again).
    Lancia Fulvia 2C 1964
    Lancia Fulvia Coupe Rallye 1,3 1968
    Porsche 924 1979
    Alfa Romeo 33 1.4IE 1993

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    Re: Relaxing an overly-tight throttle return spring

    I know exactly what I’ll do: I’ll turn up a couple of 'wheels' out of pure Teflon (can’t remember the acronym for it). That should do the trick nicely. ........so much to learn when a new car comes into your life—but that’s what keeps it interesting. Thanks again, all you experts!
    Thor Frohn-Nielsen
    '72 Lancia Fulvia 1600

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    Re: Relaxing an overly-tight throttle return spring

    Just in case someone needs a good slidey surface such as I do on the back of the gas pedal, pure Teflon, known as PTFE, is available in different diameters of round stock, and also as strips. It's easy to work with and turns beautifully on even the smallest lathe. It’s inert, strong, durable, and slippery. It should make perfect 'wheels' for the back of the pedal.
    Thor Frohn-Nielsen
    '72 Lancia Fulvia 1600

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    Legendary Lancista lancialulu's Avatar
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    Re: Relaxing an overly-tight throttle return spring

    Quote Originally Posted by Professorgearhead View Post
    I know exactly what I’ll do: I’ll turn up a couple of 'wheels' out of pure Teflon (can’t remember the acronym for it). That should do the trick nicely. ........so much to learn when a new car comes into your life—but that’s what keeps it interesting. Thanks again, all you experts!
    Microball bearings is the recommended fix for the pedal. I think it is6x6x19 (bore 6mm), but someone may know exact part...

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