Tractor Repair: Ford 4000-Carburetor, makanda illinois, bush hog

Question
Last year I put a new Zenith carburetor on my Ford 4000, 3 cylinder gas tractor and it immediately ran great! I did not run it much through the winter, and now when it runs, if I give it gas between 1/2 and full on the throttle it is making a surge type of action-low to high revving of the engine.  It only seems to do this when I give it gas past the mid-point on the throttle.  I am concerned when I start mowing in rough stuff that when I need to set the throttle to high, it will start the low to high surge action.  I did mow some over the weekend, in low 4 and at half throttle and it ran fine, but it was a very light mowing load with a 6'Bush Hog SQ 72 finish mower.  The other concern I have is that I noticed before I stopped mowing, that when I would go up a slight grade the oil light would flicker, come on, and then once the terrain leveled out would go off.  If the tractor was going slightly downhill, the light did not come on.  Once I parked the tractor on level ground, the dipstick said the oil level was good.  What are your thoughts on this issue.  Thanks so much!  John Otey, Makanda, Illinois

Answer
Hello,

  It sounds like the governor either needs repair or adjustment to fix the surging problem.  Sometimes carburetor adjustment can cause it too.  As for the oil light, the oil pressure should be checked with a gauge to verify what the pressure really is, and if there really is a problem or if the oil light is not working correctly.  It could be a problem with the sending unit or the wiring to it which would make the light come on when it should not.  If so, then the gauge should show good pressure all the time, regardless of terrain.  If the pressure is low or does fluctuate with terrain, then possibly there is a suction leak on the oil pump pickup tube.