Model D not running good under load

bosco1

New User
hope someone can help me out. minor rebuild on 8964 Zenith carburetor.runs good at idle and level down hill. coughs and backfires uphill or under small load.cleaned gas tank as well as I could. extended tank outlet so take can't run empty.
and put in line filter and gas line.any suggestions??
 
Its starving for fuel somewhere. The intake isn't leaking is it? The other thing I have seen on my DC, is the gasket where the carb bolts up. I have also had to back the fuel mixture screw out a whole bunch more then what is recommended.
 
bet you got champion spark plugs in it ,, may as well put a grese rag in the spark plughole or a tampon,you will get the same result ,,THROW THEM PLUGS AS FAR AS YOU CAN .. get autolites , search the archives under spark plugs to get the best one suggested by others ...
 
some of these modern filters are not made for gravity feed and require fuel pump pressure ,tite gas tank caps and low fuel levels with such filters have caused my 730 gasser to give me a last round warning when the gas gets low , if it were mi ne ,unless you have a filthy tank I would remove filter for now and chek results ,, fix and trial one thing at a time ,, seafoam and lucas fuel additive will help
 
The fuel systems are very basic. Weak spark issues will send you chasing carb overhauls for ever. Under load, the combustion chamber is full of fuel and air, it takes a much hotter spark to jump a gap then under light or no load conditions. Plugs could be an issue by I'd bet the farm on a weak mag. Over the years I've replaced all my magnetos with distributers and 12v alternators and have very reliable older tractors
 
I have seen this same condition as well worked on a carb till I was blue in the face finally pulled another carb know to be good and found it was a mag problem
cnt
 
thanks for all the suggestions! This tractor had the same problem before I rebuild a carburetor. so I think I will chase after the spark.which direction do I go for 12 volt conversion if I do so.? the serial number on my model D's is 5003699 what year would that be?
 
With my DC every once in a while I have to get off and reset the rod that is on the bottom of the carb the one with the rod through it cant remember what it is DRAT OLD AGE. Dale
 

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