Briggs 3.5HP starts then dies (Yes, diaphragm was replaced)

[Johns_Pop]

We took the fuel line off and tried gently blowing air through, thinking the float was stuck and it wasn't drawing fuel. We cranked it up and thought HEY, then AWE.... when it quit. I remember your advice to try priming it while it was running so we fired it up and tried that. That kept it running and after a few pumps it kept running. When I got it home and went to cut grass, nothing but prime and cut off. So I pumped it a few times on the second crank and it kept running and I got my yard cut. You think something is drying out and not getting "wet enough" to work until it's drawn fuel a while? I don't mind this if this is what I've got to do, just curious on a brand new lawn mower.

 

[vogtrj]

Could it be bad gas? I've seen your exact behavior with a couple mowers on old/bad gas.

 

[clannorm@yahoo.com]

I got a free mower from my neice who said it was hard to start. I poured a bit of gas in carb and it started for a few seconds. 2nd time when it started i put palm of my hand over top of carb and momentarily it had a vacuum in system. When i took palm of hand off carb it ran fine. End of problem till i hit one too many rocks and bent the crank. I've done this trick before and it sometimes works. theory is its going to suck some crap out of some small holes and clean carb out. It can't hurt and might help.
On same problem i've had to replace diaphragm or take carb off and clean off the screen to the pickup tube to carb. Sometimes taking it off every time engine starts to bog down.
To check if gas tank surface if flat place it on something flat like glass and use feeler gauge.