Farmall 400 Help Please!

Anonymous-0

Well-known Member
Have a 55 400 that will idle just fine, but when we pull out the throttle, it runs very rough and kind of stumbles around a bit. Almost sounds like it is reaching for more fuel. With that being said, we cleared out the fuel line, took off the carb and cleaned it up real good. Found some gunk in there but nothing too much out of the ordinary. Put it back together and....same thing...it will idle not bad, but from half throttle on out it does not run very smooth at all. Not sure if it could be a timing or igniton issue? Put new points/condenser in it about a month ago hoping that may have been the problem but no solution there either. Checked the point gap again today and reset it to be sure. Going to change the plugs and wires next and see what happens there...starting with the 'easy' stuff first. Any thoughts or ideas out there would be very appreciated. We do have a straight chrome pipe on it and was wondering if the back pressure from a muffler would help any? Just a thought that was given to my by my father-in-law. Please feel free to get back to me with any suggestions...hoping to get it running tip-top as we want to take it to a pull coming up very soon!
 
Did that. 5 turns out is wide open and was out that far and even beyond so it would let in max fuel...no difference
 
(quoted from post at 20:11:19 08/22/10) Have a 55 400 that will idle just fine, but when we pull out the throttle, it runs very rough and kind of stumbles around a bit. Almost sounds like it is reaching for more fuel. With that being said, we cleared out the fuel line, took off the carb and cleaned it up real good. Found some gunk in there but nothing too much out of the ordinary. Put it back together and....same thing...it will idle not bad, but from half throttle on out it does not run very smooth at all. Not sure if it could be a timing or igniton issue? Put new points/condenser in it about a month ago hoping that may have been the problem but no solution there either. Checked the point gap again today and reset it to be sure. Going to change the plugs and wires next and see what happens there...starting with the 'easy' stuff first. Any thoughts or ideas out there would be very appreciated. We do have a straight chrome pipe on it and was wondering if the back pressure from a muffler would help any? Just a thought that was given to my by my father-in-law. Please feel free to get back to me with any suggestions...hoping to get it running tip-top as we want to take it to a pull coming up very soon!

You may still have some gunk in the carburetor. There is a place where that stuff likes to hide and a normal soaking and cleaning will not get it, but I think your problems are ignition related. Definitely install new 388 Autolites as well as new copper core plug wires, and you might consider replacing the coil as well.
 
That main jet may be plugged. I would soak that carburetor in Carb cleaner and use compressed air to blow out the jets. Also remove that fitting on the carb where your fuel line connects and look for a screen behind it that may be plugged. Hal
 
Chris, One other thing that was not mentioned. Had a similar problem with a 350 I bought. Rebuilt carb, ignition, etc. Problem turned out to be the intake manifold gasket. You could adjust the carb to run good at idle but then when you open the throtle, it would stumble and seem to miss. Al
 

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