I have a 5hp 140220 i think is the model, its leaking gas and its coming from either the diaphragm i just replaced, or its coming from between the crab and tank, has anyone had a issue with the diaphragm leaking around the bottom.
I think your model number should be 130220.Those B&S carbs can leak from either place that you mention,usually unless your on pretty rough terrain,they only leak from the tank gasket when the tank is pretty full.If your sure that you have the diaphragm in correctly and didn't strip either of the bottom holes and are sure that you got the screws tight,you could try taking the plate back off and surface it,take a piece of glass,like a window pain and lay a sheet of 400 grit sandpaper on it,then rub the gasket surface of the plate on the sandpaper to smooth the surface and then try it again.
It's likely the tank to carb gasket thats leaking,due to the tank or carn being warped some..doubling up the gaskets can help,sealers usually wont last there though,under constant immersion in gasoline..
I have made gaskets out of an old tire tube or sheet rubber neoprene like rubber roofing in a pinch for my tiller,that has the same Pulsa-Jet carb ,which caught fire once from leaking there!..it worked great,bone dry ever since,and I also think the engine now runs better than ever before,probably air got sucked in as well as leaking there,and reduced the amount of fuel drawn in ..
well i got that issue fixed it was the tank carb gasket, now it will run for about 4-5min on full speed then just quit if i hurry up and slow it down to idle it will stay running, sorry the model number is 140202 just looked at it today.
Sounds like you may have alot of rust or other junk in your tank that is slowly plugging the fuel pickup screen. Empty the fuel out and shine a small flashlight in there, I bet theres alot of rust and maybe even sludge.
Sure the gas cap vent is not plugged up?..the diaphram only goes in one way,so its unlikely you screwed that up!..there is a little "well" in the gas tank that often rusts out and then gas wont fill up in it like it should,that can cause running problems too..a thread was posted here not that long ago on Pulsa-Jet carbs,search for that and it might be helpful..
Some Pulsa-jets had a metal BB or ball bearing thing under the screen on the fuel pipes that go into the tank that act as a check valve--if one is missing or not sealing good it'll give problems too..I'm not sure if one or both pipes had them,I know some models had none..