Trace back from the lower carb. where the cam linkage attaches to the tower, you will see a funny shaped aluminum part. on it will be a fillister head screw held from turning by a locknut. Loosen the locknut with a 7/16 wrench and turn in or out the screw to adjust the idle speed. The engine should be off to loosen the nut because it is easier to do if the linkage is in wide open throttle position. Move the screw about 1/8 turn at a time--a little goes a long way. When the idle is correct --700-750 RPM in forward gear in the water, tighten the locknut.
If its a black 125, in the middle of the tower shaft along side the block..its one hard SOB to see if ya don't know what your looking for...everything painted black there, and its more or less behind the shaft, facing forward
