Outdoor Power Equipment and Small Engines - Stumped by B&S

Hello all my first post here. I am completely stumped by my B&S Generator - 5000w 10hp. Cranks fine runs well until you put a load on it. Then in a few minutes or so depending on how much load it seems to ""run out of gas". If I put a couple of psi to the gas tank it will continue to run just fine?? Here is what I have already done.

Replaced the carb - set the float slightly higher than factory
New Plug
Removed the head - cleaned (not really very dirty) Reassembled
Checked valve clearance per B&S specs - OK
Cleaned fuel tank
Replaced everything from the tank to the carb including the tank outlet and valve.

This model does not use a fuel pump - it's strictly gravity feed.

Model 19G412 Type 1187-E1

I've never had so much trouble with a single cyl ICE!:wall:

Any thought or ideas? Is there a fuel pump that can be fitted to this model? TIA

This may be too simple, but it is possible. Check the gas cap to ensure it is venting. Loosen the cap and see how the engine runs. If the problem corrects itself, repair or replace the fuel cap.

You will probably need to set the float to correct height as it may cause problems.

If this is not the problem a leakdown test would be my next step.

I agree with Airman. Gas cap vent is most likely plugged. You can clean it or buy a new 1. Caps are cheap money.

When I first read the replys about the cap I said to myself - Already checked that. Then since what I was doing wasn't working I checked the cap (agian). That was the problem!! :)The cap has some type of check valve in it that was malfunctioning. I could blow through it but it apparently wasn't opening by the vacuum of the fuel draw down. Thanks for the help!!