Small Engines (Lawn Mowers, etc.): wisconson 7 hp engine Model 7-hd, air fuel ratio, bolans

Question
Hello  I've got a older Bolans riding mower with a wisconson engine that starts to run rough after 20 to 30 minutes of cutting grass I've had this carb apart many time cleaned it put a new carb kit in and still is acting up. when it is cold i have set the high speed for 2 1/2 turns out and idle 1 1/2 turns out like the instructions say.  It starts up ok runs at high speed ok.  After 20 minutes it starts to spit an sputter an bit eventually enought to stop cutting grass and slow engine down. It is running rough now.  so i adjust idle screw in and it runs smoother as i close it.  I then back it out now about 1/2 to 3/4 turns and its running smooth. I the run it at high speed and slowly turn in the high speed to about 1 1/2.  But it just doesn't seem to have the power it had earlier. Is there a chance fuel getting past the idle jet somewhere?  Is there a chance the gasket is leaking or a chance the carb is warped. I have put a new spark plug in and noticed is was carboned. When i replaced the kit i did not replace the float. It was a hard plactic. it seemed ok.  The only thing i noticed was the original stainless needle and brass seat and the jober kit had a brass needle with a rubber tip and brass seat. Could the be a coil problem.  Hope you have an answer because I am lost on this problem. Thanks  

Answer
 Hello John:

 From what you are Telling me, I will have to say its Bad Rings. You are Using the Carb to Compensate for the Changes in the Compression as the Engine Heat and Expands. Also the Power is another Indication of Bad Rings. Good Job on keeping it Running by Changing the Air/Fuel Ratio.
Hope this Helps.

 Good Luck

 Respectfully

 John