Small Engines (Lawn Mowers, etc.): John Deere LT 160 bogs down, blown head gasket, spindle bearings

Question
I have a JD LT160 that bogs down only at high RPM's.  This started after I was bagging leaves.  I have replaced the air filter, fuel filter, changed all fuel, changed oil, sprayed carb cleaner into the carb (Without removing it).  

I also checked to see if it was the vent in the gas cap.  With all this done - I am still stuck with the same problem.  At high RPM it bogs down and sputters with black smoke.  

I don't know how to remove the carb, and it seems the carb can not be adjusted.  Any ideas?????

Answer
It might that be your engine related if this happened while you were bagging leaves I think I would start checking underneath to be sure that nothing else is not causing the engine to load up.  Start with the PTO in the belt then spindles and spindle bearings.  From there go to drive linkage adjustments and disc brake adjustment.

If this is not the cause I would check things like blown head gasket air leak in the crankcase at the dipstick or oil fill tube.  Then check the breeder and the breeder gasket.  I would then check intake manifold gaskets and the intake manifold for any damage.  Then go back to your carburetor remove it clean every passage with a wire from a wire tie and blow them out with carburetor cleaner and compressed air.  Replace the carburetor kit and moaning gaskets.  I think that somewhere along this path you will resolve your issue.  Good luck on your project.