Small Engines (Lawn Mowers, etc.): John Deere Model 112L (hydrostatic), cast iron cylinder, john deere model

Question
QUESTION: I have a John Deere 112L Riding Mower that will only start at half throttle. When I attempt to throttle up the engine spouts and sputters and even blows some black smoke. The same is true at low throttle (idle).

ANSWER: Hi Dale,
I'll need to know what brand engine with engine model and spec numbers if it's Kohler,Kawasaki or Tecumseh. Model, type and code numbers if it's Briggs. If you can't find the numbers, I at least need to know brand, number of cylinders and if it is overhead valves or not.
Thanks,
Keith

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QUESTION: Keith,
     I could not find an ID Plate or anything indicating the Brand of engine other than the following info:

         FB460V
         Full Pressure Lubrication
         Cast Iron Cylinder Liner

Answer
Dale,
By the number, I know you've got a Kawasaki engine. It sounds like the engine is running rich. Easiest things first. Check for;
1 - clean air filter
2 - choke stuck in closed position
I would bet on #2. Especially if the problem started all of a sudden.
Does the engine oil have gas in it? If it does it will be very thin, even when cold. It will need to be changed or it can damage the engine bearings
If it were a internal carb problem, chances are it would be leaking fuel when not running. Look for these two things and let me know.
Thanks,
Keith