The little diad is the low end adjustment cap. If you pop it off you will see a small hole where the fuel goes through. You'll also see that it is very sensitive to adjustments. For starters, set the low end cap so the mark on the inside and outside are lined up. Turn it clockwise (toward the '-') to decrease the fuel and lean the low end mixture. I have a pump on my Moki so my high end is about 1-1/2 turns out. If you don't have a pump, try 3 turns out to start with. Even if the engine is sloppy rich it should still run. Remember to get the carb really wet to get the engine started.