There are two different fuel pumps depending on SN of the tractor. Either the vacuum style, or the mechanical style.
http://www.cubcadet.com/equipment/AR...0-A/0035700028
Fuel pump over pressure it possible, but if it's a vacuum style pump designed to work on a carbureted motor, I doubt it is. More likely that the needle valve isn't working as it should, or you have a weak spark. You need to figure out which it is.