Ford 1951 8N

[rbuckel]

I acquired this 8N a few months ago, and it sat for about 40 years in a barn. It is running, but I have issues with the governor. It seems the lever nearest engine will cause engine to die when it seems to go too far forward when the throttle is brought back to the idle position. Is this a governor problem? Carburetor is rebuilt.

 

[wore out]

The carburetor has an idle mixture adjustment and an idle speed adjustment. Start there.

 

[Royse]

I think wore out nailed it. I would start with the idle speed
adjustment screw in the linkage on the engine side of the carb.

 

[Tim PloughNman Daley RIP]

Yes, as stated by the others, start by getting your Essential Manuals and going by what they say on setting Main, Idle Air, and Throttle settings. Operator's Manual and the I&T FO-4 Service Manual are required reading. Don't have them? Best investment to make on your new tractor. Did you rebuild your OEM Marvel-Schebler TSX-241 carb or install a newer foreign made piece? On N's prior to 1950 with the Proofmeter, you may need a tach to determine engine speed. Here is a method developed by Bruce(VA):


MARVEL-SCHEBLER TSX CARBURETEORS FORD TRACTORS HOW TO ADJUST

When adjusting the carb, turn main jet out 1-1/2 turns and leave it. Then adjust side pointing idle mixture screw to fastest idle, not smoothest. This procedure has to be done when the engine is really warmed up and often takes 2 or 3 tries. When you turn a screw in or out, watch how may turns you go, best to only go 1 turn at a time, then WAIT for the engine RPMS to catch up. The proper method is to make adjustments while under load and at certain rpms, but early 8Ns have no Proofmeter to show R's so best guess scenario takes over. Both Ford and Marvel/Schebler say to set both the side-pointing idle mix {Idle Mixture Adjustment Needle} and the down-pointing main jet {Main Power Mixture adjustment Needle} to 1-turn as a starting point. I set the down-pointing main jet {Main Power Mixture adjustment Needle} to 1-1/2 turns and don't fool with it anymore.

Then adjust the side-pointing Idle Mix {Idle Air Mixture Adjustment Needle} for fastest idle; not the smoothest idle. Next, adjust the behind the carb idle-speed (throttle) set-screw for very slow 400-rpms idle. Do that idle mix {Idle Air Mixture Adjustment Needle} adjust for maximum idle at least 3-times. Do it like this:

1. Adjust idle mix jet {Idle Mixture Adjustment Needle} until RPM increases

2. Adjust idle-mix set screw {throttle idle-speed set screw} until the engine nearly stops (as slow as you can get it unless you have a tach that tells you 400 rpm)

3. Grasp the rod between the carb & governor & twist/shake it slightly; the slop in these rods often stops the adjustment cam from moving.

Repeat steps 1 - 3 three times with about 10-15 minutes between tries.

Remember the side-pointing idle mix {Idle Mixture Adjustment Needle} is out for lean, in for rich.

The Main Power Adjust needle is CW for reducing fuel (leaner) and if fully functional will shut off all carb fuel (even idle) when screwed in fully CW to it's seat. This leans it to point that engine dies. You say that this results in backfire. Is that correct? Just before all the way in (so lean it just barely runs, I don't see that you should observe a rich-condition-black-smoke at this point. Do you see that at this point? The Idle Mixture Adjust needle is just the opposite, that is CCW leans the idle mixture. That is because the Idle Mixture Adjust needle controls AIR, unlike the Main Power, which controls fuel. More AIR (same fuel)=leaner idle mixture. CCW=more air=leaner. Main Power needle is generally not very sensitive except near fully closed (full CW), whereas the Idle Mixture needle is more sensitive.

Tim Daley(MI)