Kawasaki FA130D fuel mix screw issue

[mtibi]

Dear community,

I have a 3.1hp Kawasaki engine (FA130D). It has a Pulse Pump carburateur (with diaphragm).
Issue: Motor starts really hard. When I get lucky and manage to start it, exhaust smells like gasoline + some popping (prob. rich mixture).
I already took the carb off, checked the diaphragm(in good shape), cleaned it etc...
Then I noticed something: the fuel mix screw does not influence the engine rpm whatsoever. Even when fully screwed in the carburateur, engine still runs.
My thoughts: This needle fuel mix screw may have something. I checked it out, it looks ok.
Question: Should the engine still run with this screw fully screwed? I personally doubt it...
Would an universal fuel mix screw work? Cannot find a precise replacement.
Do I have wrong thoughts about this screw? Please see the foto below.
Pics with the screw and its hole would follow.

Thank you for your patience and advice!
Best regards!

 

[StarTech]

What is the spec number? I suspect this is a fixed pilot screw. If so it is not meant to be adjustable.

 

[mtibi]

Hello!
The official service manual for this engine mentions 1 1/4 turns for this screw.
Attached the sequence.

 

[StarTech]

Screw is PN 16014-2059.

Probably got a clog in the air passage clogging the slow jet. Cleaning the carburetor probably will solve the problem.

Air pilot jets usually requires opening up to lean.

 

[mtibi]

Interesting info!
Thanks!

Some background: this motor is installed on a Agria 5100 grass cutter. Manufactured before 1989. Bought it from someone that claimed it sat for a long time and does not know if it ran before. The gas tank was gummed up by evaporated gas. I took off and cleaned the carburetor + tank 2 times already. No improvement. Still... something very interesting happens: the engine is very dirty inside(it has enough oil that turned black). Brown dirt from the engine is being somehow pushed in the carburetor. Could you explain what causes air from engine to be pushed in the carb? I find it interesting, still I'm a newbie regarding these engines.

Thanks for your time!