Small Engines (Lawn Mowers, etc.): B&S Primer bulb blues, fuel tank cap, annoying habit

Question
I have a 3.5hp Briggs mower engine that is about 10 years old. When it runs, it runs great- always starts on the first pull. Lately however, it has started the annoying habit of the primer bulb getting "sucked" back in after about 10 minutes of running, killing the engine. A few presses on the bulb, and it pops back out and the engine will restart. What is causing this, and how do I cure this annoying habit? Thanks!

Answer
Hi Alan,

I suspect a piece of dirt has gotten lodged somewhere in the carb.  First, make sure that the fuel tank cap is venting and not causing a vacuum.  Next, remove, disassemble and clean the carb.  Probe every small hole with a fine wire and blow it out with compressed air.

Let me know how you make out.
Michael