Small Engines (Lawn Mowers, etc.): Lawn mower will not start or starts and dies in 3-5 sec, craftsman eager 1, sears craftsman

Question
Hi There..

I hope you can help me out.. I have a Sears Craftsman Eager-1 6.75 HP lawnmower (Eng model 143.016702, Eng family YTPXS.1951BA).. and here is what issues I have..

I go to start the mower and usually it doesn't want to start, on the ocasins it does start, it runs for 3-5 seconds and dies on me.  I chenged the fuel, changed the spark plug, checked for spark and it's always there when I pull the cord,.  I took the carb off and checked for junk and dirt inside, found nothing.. nice and clean.. the mower is only 5 yrs old..

It almost looks like there isn't enough fuel getting to the carb when the RPM increases and thus it dies...  any ideas what I can try next?  

Thanks a lot for helping me out..

- Hubert

Answer
 Hello Hubert:

 Check the Carb Mounting Gasket for Tears or Damage. If it Leaks this will cause this Type of Problem too. If you are Certain the Carb has Not got Varnish Built up in the Main Jet, then Check the Compression. It should be 70psi minimum. It Sounds like Varnish has the Main Jet Clogged. Have you Soaked the Carb in Carb Cleaner? Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John