Tractor Repair: IH454 Gas Overheating, lean mixture, breather tube

Question
my 4cyl gas 74' tractor overheats and loses power after about 30 minutes.  have gone through and replaced many things over the past two years (radiator, waterpump, all tune-up parts, air filter, rebuilt carb, fuel pump).  They all needed to be done.  Starts great and besides a little tap I am pleased. have been playing with the fuel needles and timing, thinking a lean mixture is causing burden.  Driving the bushhog over tall grass can bog the thing down and kill it (I usually clutch it and just let it clear it's throat, throw some smoke out the front breather tube and ease forward.  If it dies I can't get it started for an hour.  Is it too lean/rich, retarded, what?  Thanx for your support

Answer
Hello,

  It sounds like you may have a couple of separate issues.  First, if it loses power and dies under load, it sounds like it is starving for fuel.  Check the flow of fuel from the tank.  If you only get a small dribble instead of a full stream, there is a restriction where the fuel leaves the tank.  If you have already replaced the radiator and water pump and it still overheats, then replace the thermostat also.  It should not blow smoke out the breather tube.  If it does, that means the engine has excessive blow-by and is due for an overhaul.