Lawn Boy 7268 tuning trouble

Hello:

First post here. Purchased this used in 1996 for $50. Retired guy would buy all types of Lawn Boys, piece them together and sell from his garage.

It has run great until about month ago. Compression good, new coil, new plug (every spring), and put new needle and seat in. Downloaded the manual from web and set the float at factory spec. Just could never get to run right.

Carb has the air F-100 series late model with adjustable fuel flow needle valve. It's hard to start, and won't hold RPMs, runs rough. I thought the air vane spring was bad, but couldn't find on line.

Took to local small engine shop and got back today. Runs same. Ugh. They put kit in (needle, seat, gaskets, etc.) and it just won't run right.

Manual says turn needle valve until seats, then back off 2 full turns. Get engine running, then turn needle valve clockwise until runs smooth and even.

I can her up to around 3,000 RPM but still rough. Crazy thing is when i shut off gas the engine smooths out and powers up to 3,400 RPM.

I'm thinking it's running rich and i need to tighten needle valve.

Any suggestions on this one?