Starts on a prime

[plpitts1]

Good Morning, I have a 2011 B&S 10T502 0457 B1 on a Bolens mower. Fuel is fresh, oil, spark plug and air filter good. Mower starts 1st pull on a prime and dies, will keep running if I keep pushing the primer. Removed carb and saw that diaphram was distorted. Went ahead and put a new carb on with new fiber diaphram against the tank and the new gasket against the carb., (which seems backwards to me but would not prime if I did it the other way around). It came to me with diaphram against the tank. Results are the same. Tried operating the buterfly valve manually when it started but made no difference.
Thanks,
Pat

[bgsengine]

Yep, diaphragm goes tank side, gasket against the carburetor. Make sure your spring is in there correctly (sits on the nub on carburetor and centers on diaphragm) , make sure you do not overtighten the screws (causes warp) , use a straightedge on top of tank, verify less than .002 or less out of flat on carb mounting surface (if it is more, there's a repair kit, if I recall part number 391413, or you need a new tank) also sometimes doubling up on the gasket (use an old one in good condition, perhaps) helps with minor variations in warpage (close look at new gasket after carb has been mounted can show traces of where carb seats less securely, or not seating at all) Also carburetor mounting screws torque sequence is not your typical crossing pattern - you start with the screw closest to center (closest to the throttle lever) and torque in sequence counter-clockwise.. proper torque is , I believe 15 - 20 inch pounds (which feels "barely tight" doing it by hand.. just past "snug")

If it runs on prime and not after priming, likely have a problem in jetting or nozzle, or an air leak (always use new o-ring where it mounts to crossover pipe, always check crossover pipe - they are notorious for coming loose and to a lesser extent, cracking or breaking)

[plpitts1]

Thanks, I will check that on Monday, appreciate the reply
Pat

[SUKI]

Also it would not hurt to check the valve clearances.

[plpitts1]

Thanks!

[plpitts1]

Tank appears flat with a straight edge. Tried doubling up on the gasket, same results. diaphragm spring is in correct position. It's a new carb which came with new O-ring. I checked the valve clearance, intake is good at .005 but exhaust reads .012 (should be .007/.009 I believe). Could exhaust valve at .012 cause this scenario?
Thanks,
Pat