hi  getting engine idle right is very important-  if the engine does not keep and idle for a long time-it is not right-and it should come off that long idle and screem up to your rich top end setting -then your are very close to perfect-  may need some fine tweekingfor most engines on the low end and top end i use the -squeeze the fuel line method to get into the ballparkbut i do find that depending on the type of glo engine you are using-the idle will vary between almost no rise in idle  RPM -to a 2-300 RPM rise in idle  RPMthat is were the tweeking comes injust run the top end 2-300 RPM max off your max RPM numbers-that will be fine for all glo engines-i do use castor oil in my fuel  80/20 mix-and i do like to get power out of my glo stuff-and cause no damage after 20 years that way