I have an old 1020 mccormick deering tractor that we recently pulled out of the shed. I took off the carb and cleaned it up and checked out the old float and everything. I put new plugs in it and got it running decent. However, I can only start it with the choke wide open and run it with the choke wide open. Even with this, it seems like it only runs on three cylinders. I have played around with the two adjustments and sometimes I can get it to run perfect but it wont stay long when I try to push in the choke. Does anybody have and suggestions or bits of information that will help me with this adjustment? Thankyou very much for any help.