I have an all original 75 FXE and I think your throttle bracket is installed incorrectly. My cable as you can see has a metal thing at the end that the screw makes contact with. It looks like your cable is too short due to the bracket not being installed in the right place. I can't find the right cable as I need to replace mine and the only ones I can find have a ball end and not that metal thing as you can see in the pic. Having said this, I'm having problems as well after a carb rebuild. Its taking too long to return to idle. ​​​​​​​

 

That don't look at all correct to me... certainly should Not be an angle on the cable... it is a straight pull....