1975 XS idle mixture screw setting..

[katmol]

What is the correct setting for the idle mixture screw on a stock '75 XS650B? The owners manual that came with the bike said 13/4 turns out. That can't be right, it run like crap at that.

 

[5twins]

The factory spec for the '75 carb set is 3/4 ± 1/2 turn, but just as with all the other mix screw specs for the various carb sets, it is meant as an initial setting and just a starting point. From that setting, you should adjust the screws for best idle, fastest speed and smoothest running. It will probably be in that range given somewhere, but not necessarily right at 3/4. As an example, my '78 is speced at 2.25 turns but ran best at about 2 5/8 turns out.