amc49
XS400 Junkie
Yes, to confuse the innocent.
There IS a slight difference though. The mixture screw can allow curb idle to be leaner but when you open the butterfly the transfer holes that then open up are richer to act like accelerator pumps. The air screw being at the back makes BOTH of those fuel/air exit points the same amount of richness, you cannot adjust one different. Why they went to the ones in front, they are easy to adjust slightly lean to get pollution down. The drop idle speed down 50 or 100 rpm lean from best idle then affix the limiter caps thing. Then you get a clean low pollution dead idle but still have a slightly richer transition to respond better coming onto load. It helps a lot on carbs with no accelerator pumps on them.
There IS a slight difference though. The mixture screw can allow curb idle to be leaner but when you open the butterfly the transfer holes that then open up are richer to act like accelerator pumps. The air screw being at the back makes BOTH of those fuel/air exit points the same amount of richness, you cannot adjust one different. Why they went to the ones in front, they are easy to adjust slightly lean to get pollution down. The drop idle speed down 50 or 100 rpm lean from best idle then affix the limiter caps thing. Then you get a clean low pollution dead idle but still have a slightly richer transition to respond better coming onto load. It helps a lot on carbs with no accelerator pumps on them.