Question on carb adjustment

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09FordRanger
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Question on carb adjustment

Unread post by 09FordRanger » July 7th, 2022, 10:27 am

Gents, working through my first tune-up on a MUTT that I'm pretty sure was sitting forever. Up to adjusting the carb but when I follow the TM (May 82 20 manual) I was expecting a couple of adjustment screws on my carb but nothing. I can't find any adjustment screws on it anywhere. I can play and adjust the throttle and choke cables but that's not the same as an adjustment screws to set idle and mixture.
I attached the piece from the TM I was following and a pict of my carb.
Any insights on what works as idle adjustment on these carbs would be greatly appreciated.
Thanks
Carb puzzle.JPG
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Hambone
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Re: Question on carb adjustment

Unread post by Hambone » July 7th, 2022, 11:25 am

It's hidden under a metal cap on top side of carb down close to the manifold. drill thru the cap with a small drill bit just enough to break thru the cap, then pry the cap off.

rupert's
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Re: Question on carb adjustment

Unread post by rupert's » July 7th, 2022, 11:28 am

This is an adjusting screw,
Don't over-tighten it because you can crack the neck of the carb and you'll have to throw it away.
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09FordRanger
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Re: Question on carb adjustment

Unread post by 09FordRanger » July 7th, 2022, 1:27 pm

That looks like the solution. Found my counterparts. Looks like my idle adjust screw (#1) is broken. Looks easy enough to fix.

Thanks so much for pointing me in the right direction. Especially thanks for the insight on "don't overtighten it . . " I'm exactly the type of knucklehead that would do just that.
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rickf
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Re: Question on carb adjustment

Unread post by rickf » July 7th, 2022, 6:14 pm

Run the idle mixture screw in till it bottoms out VERY GENTLY! Then back it out 2 - 2 1/2 turns and that will be a good place to start from. If you set the idle mixture according to the book you will have a big flat spot at cruise speed, I generally set the idle mixture to best idle and then back the idle screw out about a quarter turn. If you still have a flat spot then back it out another quarter turn as long as it does not start to stumble at idle. This is all assuming you changed to a 180 degree thermostat already. And you have already set your valve lash right?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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rickf
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Re: Question on carb adjustment

Unread post by rickf » July 8th, 2022, 11:00 am

And how in the world did you break the idle screw off? I should have a few of them laying around if you need one but if you can't get it out you will need to replace the whole throttle shaft.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

09FordRanger
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Re: Question on carb adjustment

Unread post by 09FordRanger » July 14th, 2022, 8:28 pm

I didn't break it. Someone in the MUTTs past did it and get this - the reason the screw was busted was someone glued it in (probably Loctite based on how tight it was in there. Best I can figure is someone lost the tension spring and the screw kept moving out of adjustment so glue it in place. Someone later tried to force the screw and busted it. Wacky I know but the only thing I can think of that would have resulted in someone gluing it in. Oh well, got it out (eventually).
Thanks for the advice on adjusting the mixture screw. I'm following the -20 closely but I'll take any experience insights I can get.

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rickf
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Re: Question on carb adjustment

Unread post by rickf » July 15th, 2022, 7:49 am

Based on what you say about the idle screw I would not be surprised if you find the mixture screw was jammed in also. If you had to remove the cap over the screw on the flange to get to it then you might be safe there. If you cannot get a good idle mixture setting then that is probably the problem. Take the carb off and slide you finger in the throat of the carb over the port where the idle mixture screw would be. You can run the screw in and it will barely poke out and you will feel the tip of it. Back the screw out and you should not feel any protrusion at all, it should be smooth. If it is pushed out there then someone has jammed that screw in tight and ruined the calibrated port. At that point you need a new carb, there is no repair for that issue. At least none that would not cost 5 times the price of another carb.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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