Are the mixture screws accessible or do they need drilled?
Have you had the carb apart?
Two things right off cause rich mixtures...Choked air flow or excessive mixture (assuming you have the right heat range spark plugs and ignition timing is correct).
Choked air flow
-Throttle plates misaligned
-Clogged air filter
-Collapsed ducting
-Choke plate stuck
Excessive mixture
-Idle mixture screws out of correct adjustment
-Float out of adjustment
-Bleeding secondaries
-Float seal damaged
-Mixture screws or seats damaged
-Fast idle sticking or out of adjustment
-Curb idle set too high
Its nearly impossible to troubleshoot without being there. Its why I give so many items to check. Common stuff I used to see when I was working on gassers.
She'll, (the samurai) will run pretty good but won't idle.
Is this your carb?
https://www.suzuki-forums.com/search/390584/?q=carburetors&o=relevance
-carburetor tune-up
-Stock Carburetor Float Weight
-She LIVES!...more or less...idle question
-stall at idle
-Please help me with a carburetor vacuum tubes !
-carburettor problems
-high idle while warming up?
-the car wont idle slow
I looked at two forum pages and found those threads related to carbs for a samurai/suzuki
If you look you might find more or better.