Post Master General
Join Date: Apr 2012
Location: Bowling Green, VA
I Ride: '09 ZX6R
My '09 battery got to the end of life last summer..... when it was difficult for the alternator to re-charge it, it would surge at idle, up and down from normal idle to ~2K, and back.
Trying to adjust that out with the idle screw, I dropped the mechanical idle setting below 800 or so..... then the surging would happen when the bike was warming up.
When the engine is cold, the ECU uses a much richer default map, the same as a choke or enricher circuit would do. The ECU checks the idle speed and corrects as the engine warms and conditions change.
"Basic stuff fellas. Use your head for something other than to break your next fall."