Ford NAA idles too fast how to adjust

[Garryowen]

Ford NAA idles too fast . I've adjusted to idle screw on carburetor down to 900 RPM's. It should be 450 RPM's

 

[old]

Ford NAA idles too fast . I've adjusted to idle screw on carburetor down to 900 RPM's. It should be 450 RPM's

The carb has to idle adjustment one on the carb it self and one on the carb linkage so did you adjust the linkage one or the carb one

 

[Garryowen]

I adjusted the one on the carb from 1100 RPM to 900 RPM. Need to get to 450 RPM and I'm not sure how to get there. I did clean and install a carb kit though

 

[old]

I adjusted the one on the carb from 1100 RPM to 900 RPM. Need to get to 450 RPM and I'm not sure how to get there. I did clean and install a carb kit though

On the linkage there is an idle stop screw adjustment you need to adjust

 

[Garryowen]

Yes that is what I need to know how to do

 

[old]

Yes that is what I need to know how to do

Well it is very simple you just back the linkage adjustment till you get the idle you want.

 

[Garryowen]

Which way?

 

[Jim.ME]

As things get changed over the years, post a couple pictures of your carb and tell us what kit you used.

 

[Garryowen]

The carb number is TSX 428.

Premium Carburetor Repair Kit Fits Ford Jubilee NAA 600 620 630 640 650 660 700 740 Tractor (For Marvel Schebler TSX428 TSX500 carburetors)​

It's the original carb been on since 1953

 

[Jim.ME]

The carb number is TSX 428.

Premium Carburetor Repair Kit Fits Ford Jubilee NAA 600 620 630 640 650 660 700 740 Tractor (For Marvel Schebler TSX428 TSX500 carburetors)​

It's the original carb been on since 1953

When you rebuilt the carb did you remove the throttle plate? if so did you confirm it is centered and will close all the way?

Does this look like your carb and the adjustments on it?

 

[Garryowen]

Yes

 

[Jim.ME]

Yes

Did you confirm the throttle plate will close fully when you finished the rebuild?

You are saying that if you back the idle speed screw out the rpms will not lower?

To me that would indicate a throttle plate not closing or a linkage problem somewhere.

 

[pomester]

The carb number is TSX 428.

Premium Carburetor Repair Kit Fits Ford Jubilee NAA 600 620 630 640 650 660 700 740 Tractor (For Marvel Schebler TSX428 TSX500 carburetors)​

It's the original carb been on since 1953

Look between the carb and the engine block at the carb linkage. There is a screw/bolt associated with the bell crank - it may not be very evident if the area is a mound of oil/dirt/gasoline. That small screw tightens against a stop and holds the butterfly valve open at idle. With the tractor at operating temperature, adjust (loosen in this case) the screw until the idle drops to the right range. Adjust the idle mixture screw. Readjust the screw behind the carb. Repeat until the tractor idles smoothly at the desired rpm. Note that for a 450 rpm idle, the rest of the engine (ignition, valve adjustment, compression, etc) needs to be in good condition.

 

[Garryowen]

It's not that carb. The idle speed is on the right side next to the motor. Idle fuel/air mix is on the left side. The carb sits left to right.

 

[pomester]

Yes

It is possible to instal the throttle plate backwards - that would be an issue.

 

[Garryowen]

I followed this on YouTube

Ford Marvel Schebler Carburetor Rebuild: NAA, Jubilee, 600, 700, 800, 900, 2000, 4000
​

147K6y ago


Dan and Rachel Gingell, FarmTractorRepair
Rachel details the rebuild process for a Marvel Schebler carburetor, including adjustments. For parts, please

 

[Garryowen]

She said to leave a small fingernail gap at to top

 

[Garryowen]

The throttle plate only goes in one way I believe

 

[Jim.ME]

It's not that carb. The idle speed is on the right side next to the motor. Idle fuel/air mix is on the left side. The carb sits left to right.

Regardless of the orientation, it has the three adjustments and yes, the idle speed is next to the engine.

My questions on the throttle plate and linkage still apply.

With the idle speed adjustment backed off the plate should close the throat off. Did it?

If the plate is able to close the throat off, I lean towards a linkage issue.

 

[pomester]

The throttle plate only goes in one way I believe

It's beveled and possible to install upside down, tho it should be evident. The plate also has some adjustment such that with the screws loosely installed, you can close the throttle shaft and shift the throttle plate to tightly close the venturi then tighten the screws.