I know that the older Harleys with a carb can idle lower than the injection models; my question is WHY?? and don't give any of that oil pump not pumping enough ASO. I guess it has to do with the injectors. Having a PC III I can adjust it lower (I think....), but let's see some grey matter here, C'mon brain, I know you are there....

 

Higher RPM to maintain correct voltage/amperage for ECM and Fuel pump(it's electric.LOL). The only way I've seen to lower idle speed correctly is with the use of SERT, can lower to your hearts content, not recommended though. Idle time is minimal during riding, why bother adjusting .
Stay Safe.

 

Dunno about any of the twin cam engines, but evo engines need to be doing at least 700 to 800 rpm to get decent oil flow to develop pressure.

 

Idle for the TC's is about 850. Oil flow would be the major reason for not going lower myself. No oily, no runny.