How can I be sure my air/fuel ratio is set right.  I turned the ratio screw fully clockwise and then 2 full turns the other way.  I then started it up and waited for three min. to warm up.  I played with the screw to feel the engine for smooth or rough idle.  I then set the idle screw where I felt was a happy idle.  
I just want to make sure I get the accurate RATIO setting because I almost burnt up the engine on the smaller 110cc seaseng.  The 125cc KMD has never run hot but I want a definite and surefire way to know if the ratio is correct.  I also got new plugs for both but I have no idea what the gaps are.  I just popped them in and they both ran ok.  

sounds like you set the air/fuel mixture correctly, the air fuel/mixture screw is only for idle-1/8 thottle. the slide, pilot jet, needle, and main jet are what sets the air/fuel mixture thuout the rest of the thottle range. if it accelerates smoothly up to open thottle, then the slide, pilot jet, needle should be ok, to check the main jet you need to do a plug check. this is easy, install brand new plug,start engine, accelerate to full thottle, hold it their for a bit, then close thottle, pull in clutch, turn off ignition, slow down and stop, wait for engine to cool down, (never remove a spark plug from a hot engine) and now check to see what color the electrodes are,
white means to lean, black to rich,, tan is just right.