Tractor Repair: Diesel engine knocking, international 434 tractor, dirty fuel

Question
I have an International 434 tractor which seems to knock
excessively and seems to have a lack of power. I am
inexperienced and would be grateful of any advice as to
possible causes. Some 3 years ago I replaced the pistons and
shells but I did not have anything re-ground.  

Answer
  Noises can be difficult to diagnose sometimes.  It would probably be easiest to remove the valve cover first and check the rocker arms and push rods.  If everything is OK, then remove the oil pan and check the crankshaft and bearings. Then you can also see if the pistons move excessively from side to side or if the connecting rods move up and down on the piston pins.  Not sure if your power loss is related or not.  If the bearings are loose, it would not be related.  But if the pistons are slapping or there is something wrong under the valve cover, it would be related.  Power loss can also be caused by fuel line restriction or dirty fuel and air filters.  Also make sure it has the correct fuel in it.  Sometimes people accidentally put gasoline in instead of diesel fuel, but then they smoke real bad.