At idle the throttle cables bottom against adjustable stops on the carburetors. It is important that they stop equally or the engine runs rough and this is bad for the gearbox dogs. Over time the carburetor stops bend and the idle becomes rough. I prefer to use the cable stops to adjust my idle, this method has been more precise with no drift over time. The OEM cable stops are a collar with a set screw. They work but they permanently dent the cable which makes fine adjustments difficult besides the damage to the cable. I made these stops that clamp onto the cable, cause no damage and easily adjust.