OS LA engines have airbleed carburetors. The adjustment of the low speed is very similar, except you turn the airbleed screw in the OPPOSITE direction you would turn a low speed mixture screw.

Airbleed carburetors control the idle mixture by regulating the amount of air that enters through that tiny hole in the front of the carburetor. The screw on the right side of the carbuertor is what controls the size of the opening.

Let the plane idle for a good 10-count, then quickly firewall the throttle. If the engine dies or hesitates, turn the airbleed screw IN 1/4 of a turn. If the engine blubbers and smokes, turn the airbleed screw OUT 1/4 of a turn. Airbleed screws are much less sensitive to adjustments than idle mixture screws, so you need to move them more to see any results.

While you may not get an airbleed carburetor to ever transition perfectly, you should be able to get a reasonable transition out of it. If you find that you have completely turned the airbleed screw out of the airbleed hole, and the plane still blubbers when you shove the throttle ahead, disassemble the carburetor and drill out the airbleed hole with the next size larger numbered drill bit. 1/64" or 1/32" of an inch may be too much, which is why you need the numbered drill bits.