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Thread: Scorpion carb adjustment guide

  1. #1
    Senior Lancista ecohen2's Avatar
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    Scorpion carb adjustment guide


    I have the Scorpion shop manual, but does anyone have any good suggestions on how to properly adjust a stock carb for a Scorpion?

    I can't seem to get mine adjusted properly, right now it either idles too low or hesitates whenever I get on the gas.

    Thanks,
    Ed
    1976 Lancia Scorpion
    2004 Noble M12 GTO 3r (SOMETHING NEW!)
    http://www.lanciascorpion.com

  2. #2
    Tom McGaffigan
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    Re: Scorpion carb adjustment guide

    Ed,
    The first thing you should check is if there is any air being drawn into the carb through the secondary bore of the carb. With the car running and warmed up, place your palm over the secondary opening of the carb. If the engine RPM changes then you have air leaking past the throttle plate on the secondary. You need to adjust the secondary throttle stop on the underside of the carb. See the diagram in a Weber book for its location. It is impossible to see and almost as tough to adjust. I bent a screw driver 90 degrees and was able to back off the screw thus allowing the secondary throttle to close completely. Onece this is done you can adjust the primary throttle stop to set the idle. On a Scorpion there is very little adjustment range for the mixture at idle but there is some. Connect a vacuum gauge and adjust the mixture screw until you have maximum vacuum at your desired idle RPM. If the mixture screw has little or no effect then you might want to try going up one jet size on the primary idle jet. All this assumes you have a properly timed ignition, good plugs and plug wires. If you cant stop the leaking air through the carb you are going to have to live with it of get another carb.
    Tom McGaffigan

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    Senior Lancista John O's Avatar
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    Re: Scorpion carb adjustment guide

    Hey Ed,

    I have my stock carb off the car and will probably not need it again for quite a while if you want to give it a try. I can bring it to the Rockville Car Show if you don't want it sooner. The only problem is that I've used the jets from it in my 34DMTR, so you'll have to swap your jets over from your stock carb - should take about 2 minutes.

    John O.
    '76 Scorpion (Whoas, Springs, Konis)
    '86 Bertone-X1/9
    '82 Spider 2K (The Good Woman's, but I'm the Chief Mechanic)
    '13 Fiat 500 Abarth (mine, black w/white wheels)
    '13 Fiat 500 Abarth (The Good Woman's, red w/black wheels)
    '82 Dodge Ram D150/1500
    '74 MGB-GT (Derek's, always will be...)
    Please God, No More!

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    Senior Lancista ecohen2's Avatar
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    Re: Scorpion carb adjustment guide

    Believe it or not, I actually have a spare carb that I bought from someone on this board. This is more about getting my current one adjusted properly.

    I was reading the other day that with Webber carbs, if it hesitates on acceleration that means the "engine is starved for fuel." However, the article did not say if that means the fuel pump isn't getting the job done or the mixture is too lean. Any thoughts?


    Tom, thanks for the info I am going to give this a try this weekend.


    Ed
    1976 Lancia Scorpion
    2004 Noble M12 GTO 3r (SOMETHING NEW!)
    http://www.lanciascorpion.com

  5. #5
    Will
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    Re: Scorpion carb adjustment guide

    Hi Ed;

    Was it working before? And have you checked the obvious (vac leak in intake tract or gunk in the carb)?

    Particularly with "de-smogged" Scorpions, you are likely to find a whole host of rotted vac caps and/or bits of hose with bolts shoved in the end- maybe even a golf tee ! There are a bunch of connectors on the bottom of the stock inlet manifold that you may find are open or connected to a hose and look correct until you find the other end of the hose isn't connected to anything.Don't forget to check the EGR valve.

    My approach for solving an unknown carb problem is first to see if the idle picks up with propane, acetylene, etc. down the carb barrel (and you may find you can test that secondary this way too) and second, to unbolt the carb and flush it with solvents- because generally carbs don't go "out of whack" unless somebody's been monkeying with them, but cars that have been sitting are often victims of bad gas, sludge, and rotted rubber causing vac leaks. You might not NEED to clean the carb, but it doesn't hurt and IMO it's a lot easier to see what you are doing if it's off the car. Also keeps stray parts out of the inlet mani!

    I have Haynes Weber book if you need short-term loaner.

  6. #6
    Senior Lancista John O's Avatar
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    Re: Scorpion carb adjustment guide

    I agree (mostly).

    Your car is so very, very stock that I think what is going on has more to do with age and wear than any adjustment being necessary. My experience with stock Webers is that problems occur when they are dirty or moving parts are worn, at worst PO have monkeyed with them badly.

    Off the top of my head, I'd say accelerator pump - the diaphram is probably cracked/torn. With the engine off, take the cleaner top off and shine flashlight into the primary side. Then work the trottle lever a few times and you should see a pronounced squirt of gas from the arm that extends into the barrel. No squirt, no pump.

    Beyond that, if you personally haven'y taken the carb off, cleaned it, and replaced all the gaskets, diaphrams, etc., do not delay, clean today!

    Edit:
    Also, an easy way to find vaccuum leaks (not sure you have any) is to spray carb cleaner around the carb avoiding the barrels and jets at the top and around the intake manifold. If there are no leaks, running should remain unchanged.

    John O.
    '76 Scorpion (Whoas, Springs, Konis)
    '86 Bertone-X1/9
    '82 Spider 2K (The Good Woman's, but I'm the Chief Mechanic)
    '13 Fiat 500 Abarth (mine, black w/white wheels)
    '13 Fiat 500 Abarth (The Good Woman's, red w/black wheels)
    '82 Dodge Ram D150/1500
    '74 MGB-GT (Derek's, always will be...)
    Please God, No More!

  7. #7
    Senior Lancista ecohen2's Avatar
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    Re: Scorpion carb adjustment guide

    When I first got the car, I replaced all of the vacuum hoses with new ones. So I am pretty sure they are not leaking. As far as the hose with the bolt, I have a new bolt with a zip tie on that, so its pretty tight.

    My air intake (round plastic thing on top of the carb) was cracked and I had sealed it with super glue and electrical tape. That could be leaking again, however I do have a new/used one that I can swap in today.

    Ed
    1976 Lancia Scorpion
    2004 Noble M12 GTO 3r (SOMETHING NEW!)
    http://www.lanciascorpion.com

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    Senior Lancista John O's Avatar
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    Re: Scorpion carb adjustment guide

    Right, but you could be dealing with something as simple as a leaking gasket at the base of the carb. Ask me how I know. You won't be sure until you just go through it, do the basics, dot your i's and cross your t's.

    John O.
    '76 Scorpion (Whoas, Springs, Konis)
    '86 Bertone-X1/9
    '82 Spider 2K (The Good Woman's, but I'm the Chief Mechanic)
    '13 Fiat 500 Abarth (mine, black w/white wheels)
    '13 Fiat 500 Abarth (The Good Woman's, red w/black wheels)
    '82 Dodge Ram D150/1500
    '74 MGB-GT (Derek's, always will be...)
    Please God, No More!

  9. #9
    Will
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    Re: Scorpion carb adjustment guide

    Your air intake shouldn't matter- it's the part(s) under vacuum you need to check- everything between the throttle shafts themselves to the intake manifold gasket. Also, " just because you fixed it yesterday don't mean it ain't breoke today", in other woirds, if you got air into the exhaust or a lean backfire, you could have popped one of those new hoses or a freshly replaced vacuum cap right off the motor. This happened to me enough times I finally vowed to weld every hole in that bitch closed the next time it comes off.

    FWIW, the head temp sensor(s) are the same merric thread (14mm? dunno) as you'd need to plug the EGR hole, so you can smear some teflon on it and run it into the manifold to replace the EGR fitting. This has the bonus value of confusing the heck out of the next owner, who will be doubtless be confounded by what looks like an IAT sensor on a 1.8L carby.



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    Senior Lancista ecohen2's Avatar
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    Re: Scorpion carb adjustment guide

    Uhg..... Discovered more of the previous owners handy work tonight....

    First, the piece I always call a dashpot is missing from the carb on my car. However, I have a spare from my second carb. The difficult part is that you cannot put it on the carb without taking the carb off, I tried for hours. Is not having the dashpot going to cause a problem other than increased emissions?

    Thanks as always,
    Ed

    1976 Lancia Scorpion
    2004 Noble M12 GTO 3r (SOMETHING NEW!)
    http://www.lanciascorpion.com

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