Hi all:
I have been reading this thread and if I may add to Antique's message and throw in a question for the original poster as well.

As Antique stated. Walboro designed the carb as per the illustrated parts manual. If something is missing from the carb that should be there, it is not right. Get all the gaskets from a carb rebuild kit and ensure they are on the carb per the IPC (illustrated parts catalog)

If your carb is a side mounted carb it is always good insurance to run a tube from the carb back plate to the inside of the fuse to equalize the carb and keep it from getting pressure pulses from the prop while in flight.

For my 2 cents If everything is right with the carb and the engine is sagging off right after takeoff, May I suggest that you ensure the overflow/vent line is not partially clogged. If it is clogged or partially clogged it will cause the engine to run lean and one of 2 things can happen.

1. The engine will sag and either keeprunning or die(lean condition caused by a partial blockage of the vent line).
2. The engine will sag and die (full blockage of the vent line) if this is the case your fuel tank will collapse as well.

I had this happen to me on a maiden and the fuel tubing got next to the muffler and completely blocked off my vent tube. Engine died, fuel tank was collapsed but we made a good landing.

Dont know if this helps you or not but is something to look for.

Good luck and I hope you get it sorted out.

Glenn Williams