The only advantage to an OB is you can take it home to work on. Allso be aware that is no simpler to work on or diagnose!!
The first thing I would do is take a look under the distributor cap to check for a clean cap & rotor and be sure the centrifugal advance is working by giving it a twist and "it's" springing back smoothly.
If the plugs are sooty it means she is running rich. Take a VISUAL look at the choke to be sure it is backing off completely.
Now if you are "idling" and the air screw was out 3 1/2 turns you should be very lean and at 2/1/2 still lean. Most of these idle at around 1 1/2 turns out.
Sounds as if there may be something inside the carb plugging an air jet. But first do the above.
Have you tampered with the timing? Do you have a crisp blue spark?
Dave Neptune
