The top of the tank and the bottom of the carburetor may not be flat. However with a Pulsa-Jet that causes rich mixture (very rich indeed), not lean mixture.
There are two available cures if tank or caburetor is bowed: use the awful Briggs kit (roll pin and teflon washer), or draw file them both flat. Bob, it's time you learned the latter technique, you have plenty of parts to practise on.
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=22526#Post22526
