Small Engines (Lawn Mowers, etc.): Starter problem, solonoid, starter problem

Question
I have an older MTD riding mower.
The engine crank's, but very sluggish.
When I pull the spark plug, it cranks fine.
Both battery & solonoid are good.

Could a starter be weak?  Is there a way to test?

Thanks

Answer
It's possible to be a weak starter but I have only seen this a couple of times.

Is the battery new?  Did you clean the cable ends and battery terminals with a wirebrush?  You will have to dis-connect the cables to clean them.

Cables will also go bad once in a while.
Let me know.
Eric