Small Engines (Lawn Mowers, etc.): Lawn tractor barely turns over, volt battery, compression release

Question
When I turn the ignition to start my lawn tractor, it barely turns and sometimes clicks.  If I take out the spark plug, the engine turns over normal---it seems.
I have replaced the starter,  12 volt battery and the solenolid.  Can you help me?

Answer
 Hello Jim:

 From your Description it Sounds like the Valve Lash needs to be Set. Most Engines have a Compression Release that Assist in the Starting of the Engine. It is Internal an will Cause Problems Like this when the Valve Lash is Improper and this Release Can Not Work. Send me the Model, Type and Code Numbers, Please. With these I can Locate a Breakdown/IPL of the Engine and Better Assist you. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John