Small Engines (Lawn Mowers, etc.): tecumseh starting problems, compression stroke, battery cables

Question
i have a 16 hp tecumseh engine. the electric starter will only turn the engine over until the compression stroke then the starter stops, then very slowly turns the engine over until after the compression stroke which it then spins fast again. if i take the spark plug out the engine spins over fine. i have taken the starter apart and all the brushes and bushings are in great shape. the starter does have a burnt smell to it. i tried ohming the commutator and it shows that all the windings are shorted (very, very low reading). not sure if that is right. could the starter just be weak? thanks

Answer
How old is the engine?  Did the problem happen suddenly or has the engine sat a while?

What is the engine on?  I have had battery cables that were too small or too old which caused too much current loss producing a weak starter.  Actually, I rarely find bad starter.  Usually poor/old wiring/cables, valves out of spec, too much engine oil, and I have even seen carbon build-up cause this problem.
Let me know what the engine is on and how old it is.  You can also check the internet for measuring for a voltage drop across cables to isolate bad cables.
Eric