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Carter YF choke adjustment

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rratselad
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Joined: Sat Apr 02, 2016 11:45 am

Carter YF choke adjustment

Post #1 by rratselad » Tue May 19, 2020 5:07 pm

Hi All,

I'm hoping someone will take pity on me and tell me what I'm doing wrong. New Carter YF is going on my 1970 240. I'm trying to follow the 1970 OE manual for adjusting the automatic choke. It's not making any sense to me after reading (and re-reading) the manual several times, while also studying the linkage and how it works. The Hayes manual is worthless and doesn't cover the 1bbl carb at all.

Here's a link to the page in the 1970 OE manual I'm trying to follow.

Here's my problem:
I follow step one. No problem. When I get to step 2, I continue holding the choke plate shut (it doesn't say to let it go). As a close the throttle, the butterfly plate completely closes b/c the spring pulls it closed. In looking at the linkage (fast idle cam, etc.) I don't see how any bending of the fast idle link will affect the throttle plate position based on the position of the choke plate. The only way I see the linkage doing anything is that if the throttle is wide open, it forces the choke plate open a little. Why is the manual having me play around with the choke plate at all?

I have to be missing something...? Thank you!

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68Flareside240
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Location: Selma, AL

Re: Carter YF choke adjustment

Post #2 by 68Flareside240 » Tue May 19, 2020 6:01 pm

So I have not fooled with the auto choke on a YF/YFA as mine was manual choke, but I have fooled around with the 2150 climactic choke and it appears to be more complicated than the YF, as far as moving parts go. While completely different, remember the choke is just to limit the amount of air to an engine, in order to richen the mixture until the engine is up to operating temp.

To set the choke on an auto choke engine, you're supposed to slowly put the accelerator to the floor, and slowly let off. This gives a squirt of fuel from the booster into the intake, and sets the choke mechanism. This is what it is asking you to do in the first step, to set the fast idle cam where it is supposed to be. The drill bit is just a feeler gauge for the throttle bore to throttle plate clearance. You bend the rod until the throttle plate stays open to that amount (with the choke ON).

rratselad
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Posts: 29
Joined: Sat Apr 02, 2016 11:45 am

Re: Carter YF choke adjustment

Post #3 by rratselad » Tue May 19, 2020 8:56 pm

Thanks Flareside!

In moving the carb linkages and plates around, I'm not seeing what happens in step 1 actually impacting step 2 on this particular carb. This is really where I'm lost. With the Carter YF, I'm not seeing the position of the choke can actually affect the position of the throttle plate. The throttle plate can affect the choke, but not the other way around (or I could be missing something).

The dechoke clearance measurement/adjustment makes sense and I can get the carb to behave accordingly on a bench.

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68Flareside240
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Location: Selma, AL

Re: Carter YF choke adjustment

Post #4 by 68Flareside240 » Tue May 19, 2020 9:19 pm

Even having the carb in front of you, it can be difficult to figure out the way things are supposed to work. I know I poured over info numerous times on the 2150 trying to get the choke right. But I finally got it. Remember, all these settings and adjustments work together, and there’s a method to set them. When one thing changes, need to check everything to make sure it works together.

One thing I think may have been missed is to turn the choke thermostat housing all the way towards the rich direction (counter clockwise). This winds the spring inside the choke housing up simulating really cold conditions, and “loads” the choke system up. This is essential to getting the settings right.

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bubba22349
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Re: Carter YF choke adjustment

Post #5 by bubba22349 » Tue May 19, 2020 9:24 pm

If it's a new carb those settings in your manual should have already been factory set. If your rebuilding the carb yourself then set them according to the instruction sheet in your carb rebuild kit. After the carb is installed on the engine with a new base gasket. Hook up the hot air stove pipe (with its insulated cover) running from the exhaust manifold up to the carb's choke housing to provide heat to the thermostatic spring in the choke cover. Next check that the Choke cover is set to 2 Rich, i.e. past the center Idex Mark. Now when the carb's throttle lever is opened the thermostatic choke cover spring pressure is acting on the choke linkage going to the fast idle cam it should then set itself to the high point of cam.

Start the engine and set the fast idle screw so the engine is Idleing at 1200 to 1500 RPM (with your air cleaner installed don't forget the air horn gasket) you want just enough engine RPM so the engine will take off good from a stop without stalling. With an Automatic trans you may need to have that higher RPM setting of 1500 over that used with a Manual trans at 1200 so test this out by experimenting and adjust as needed for good drivability when the engine is cold.

As the engine is fully warmed up to its normal operating temperature remove the air cleaner lid and check that the carb's choke blade is now fully open. Recheck the choke blade setting again when the engine is cold by stepping down on the throdle pedal all the way and releasing it, the choke blade should now be closed the amount can vary and will depend on the ambient air temperature acting on the thermostatic spring applying pressure to hold the choke blade closed as well as acting on the fast idle cam to reset it to the high point. If it's is operating correctly then your all done, if it's not then make minor adjustments to the choke cover setting by another notch more rich or go lean / less if your local area has hotter weather. That's about all there is in setting up the Auto Choke. You may also find the short video below helpful in understanding how all the choke parts work. Best of luck :thumbup: :nod:

Cater YFA Chokes
https://m.youtube.com/watch?v=AYajHO23UeY
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

blprice74
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Location: Clemson, SC

Re: Carter YF choke adjustment

Post #6 by blprice74 » Tue May 19, 2020 9:34 pm

Bubba may have beat me to it, but this guy knows his stuff.

https://youtu.be/AQq1EWFz_c0

Brandon
1978 F100 Custom. Flareside. Inline 6-300. 3 speed on the column.

1986F150six
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Location: Northwest Alabama

Re: Carter YF choke adjustment

Post #7 by 1986F150six » Wed May 20, 2020 12:03 pm

This old thread details an adjustment made on my 1986 F150 with 4.9L engine. I hope it will help.

https://www.ford-trucks.com/forums/1110 ... 101-a.html

Lazy JW
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Re: Carter YF choke adjustment

Post #8 by Lazy JW » Sat May 23, 2020 9:22 am

I like to adjust my chokes on a nice, balmy 70 degree afternoon when the engine has not been started that day. I adjust it until the choke almost, but not quite, closes completely. When it is warmer, it won't close at all, and when it's colder, it pulls more tightly closed.

Those perfect conditions occur about once every three years around these parts ;-)
"The White OX" 1974 F-350 300-6, Stock single exhaust, Carter YF, T-18A, Dana70 w/4.11, Flatbed dually w/dump bed. "Where no oxen are, the crib is clean, but much increase is by the strength of the ox" (Proverbs 14:4)
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