Small Engines (Lawn Mowers, etc.): carb issues, hp briggs, vacuum leak

Question
i have an 8 y/o, or so, craftsman mower with an eager-1 6.5 hp briggs.  the rpms run up and down as if it is starving for fuel.  i have replaced the breather hose to the intake "box" and have cleaned the carb.  nothing seemed bad.  here is where i am puzzled.  the mower runs great when you depress (hold in ) the primer bulb.  i hit the bulb a few times to prime, start mower, and continue to hit bulb, and then must keep and hold bulb pushed in.  the gasket is worn but i sprayed carb spry near the gasket and didnt change the rpms.  i thought it was a vacuum leak there.  please help.  i just dont want to spend $350 for a new mower that has a problem that i know i can fix, most of the time.  thanks

Answer
 Hello Jason:

 This is a Common sign that the Main Passage and Jet Inside the Carburetor is Restricted with Varnish. To Properly Clean the Carburetor; Remove and Disassemble the Carburetor. Soak it Overnight in Carburetor Cleaning Solution(I use Gunk) and then Blow Out the Passages with Compressed Air. Install New Kit and Primer Bulb. Spray Cleaners Will Not Clean the Varnish Out of a Carburetor. They Just Loosen the Top Layer of Varnish and Usually Cause More Problems with the Carburetor. If you Require a Breakdown/IPl or Other Assistance; Send me the Model, Type and Code Numbers Off the Engine, Please. With these I can Locate a Breakdown/IPL 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