B&S intek 4155 15.5hp running rich

Intek 15.5hp running rich .
Black smoke when operating throttle and under load ,bogging down on full throttle, 3/4 throttle ok.
New carburetor, filters, spark plug & oil .

No difference between new and old carburettor.

Carburettor order part nr 594593, carburettor marked 595210

ruixing carburettor

Can this really work on 14- 21hp engines ? The jetting might be to big for my 15,5hp

Anyone with knowledge?

The NIKKI carb, IMO, is junk due to the design.  The other is of standard design.
 
You may want to pull the float on the Ruixing and check for any leaks in the float.
That would cause the float to stay open.  You may also have a piece of crap between the float needle and seat, so remove that and make sure it's clear.
 
Also check the main jet (down the center, extended part of the carb, under the float bowl mounting screw)
 
That carb should work fine.
 
If you have a vacuum brake bleeder, attach it to the carb inlet, hold the carb upside down and check to see if it'll hold a vacuum.  It should...   
 
Lastly, remove the entire carb and hook up the fuel line and put fuel to it.  Make sure there's 
no fuel leaking/trickling from the carb throat.
 
 
.