Small Engines (Lawn Mowers, etc.): Lawn Mower Dies - crankcase breather or exhaust valve?, crankcase breather, exhaust valve

Question
Hi Michael,

My mower has a B&S Quattro 4HP engine. I recently cleaned the carb and it ran well for several months.

Now it starts fine and runs for a couple of minutes but as it runs, the air gets sucked out of the primer bulb and once the bulb gets sucked in, it dies. If I pull the bulb back out, I can restart it no problem but the same thing happens.

Obviously an air inlet somewhere is clogged - I was told possibly the crankcase breather or exhaust valve. Any suggestions? If it's one of these, how do I locate them (I don't know those two).

Thanks!

Answer
Hi Andrew,

The primer bulb fills with fuel only.  If it doesn't refill, then I suspect that the carb most likely has dirt, debris, or gummed fuel inside.  You will need to remove the carb, disassemble it, clean all the small internal openings and blow it out with compressed air.   Probe each and every hole with a small wire.  A carb rebuild kit wouldn't hurt either.

Let me know how you make out.
Michael