"These engines are not differe
"These engines are not different than the 'old' ones when it comes to idle adjustment. On the old ones, you mainly adjusted the timing advance by moving the trigger/sensor coil, here you move the optical sensor which is equivalent. Just be sure that your carbs are completely closed!
Moving to -, means you are reducing timing advance at idle. In 80% of cases the factory setting works out, but depending on mainly water level on the leg (exhaust back pressure)it might be needed to adjust.
Move it 1 'notch' at the time until you are where you want to be.
Personally I always did a de-carb (Sea Foam/Engine Tuner) on the engine before adjusting anything."