F-20 Question

After adjusting the points in the mag it fired right up, ran smooth for a bit, then died. Got dark out and I didn't have any more time to mess with it and haven't had time since....finally quit raining here so it's time to make hay. I know I could probably figure this out by myself in time, but just thought I'd post here and see if anyone(Cowman?) could steer me in the right direction.

What the deal is- it'll start and run for a second then sputter and want to die. I found I could keep it running by pulling the choke almost completely shut. Then I open the choke and it'll smooth out for a second then almost die again until I pull the choke shut again. Obviously it's not getting fuel. Has a good stream of fuel from the fuel line at the carb and the screen in the carb inlet is clean. I also drained the old gas and it has fresh fuel in the tank.

My thoughts- 1- a jet or passageway somewhere in the carb is plugged up(I have a new carb kit sitting here that I haven't installed yet and a 5 gal. bucket of carb cleaner so if that's the problem it'll get fixed when I get time). Or, 2- The intake manifold gasket isn't sealing and it's letting enough air in that it needs the extra fuel from choking it to run. I put the gasket on dry out of the box(knowing that most gasket sealers and fuel don't get along well together). Haven't yet tried spraying carb cleaner around the gasket to determine if it's leaking but that's next on the list.

Is there anything else I may be overlooking here? Any special tricks to sealing up the manifold gaskets on these engines? This is the original dual-fuel manifold, not an aftermarket peice.

Any advice will be appreciated! Alsp- if anyone knows a baseline setting for the fuel mixture screws on the carb, that'd be appreciated greatly too!

I found F-Dean's advice to turn the gas all the way on interesting. On all the tractors I've ever driven that had that style of sediment bowl setup, from the Super A to H's, M's, this F-20 back when I first got it, and all the way to our 656 gasser, I've never run any of them with the valve opened more than a turn or two. Usually they worked fine. Guess it's worth a try though!

I found F-Dean's advice to turn the gas all the way on interesting. On all the tractors I've ever driven that had that style of sediment bowl setup, from the Super A to H's, M's, this F-20 back when I first got it, and all the way to our 656 gasser, I've never run any of them with the valve opened more than a turn or two. Usually they worked fine. Guess it's worth a try though!