Motorcycle Repair: 1989 FXR, neighborhood roads, butterly

Question
1989 FXR - rejetted butterly Keihn, Supertrapp 2 into 1. otherwise stock. (both mods long ago).
Within the past 3 months have developed an intermittment coughing/sputtering. Running fine on neighborhood roads or highways, suddenly operation acts like "75 percent", then will return to normal. No specific duration, no particular circumstances before onset. All electrics except plug wires, stator, and battery original equipment.  

Answer
First I would check the intake for a leak. Start the bike and let it warm up. Spray a little carb cleaner around the intake while it is running. If the RPMs go up you have a leak.
Next check for a short in the ignition wiring.
If that in not the problem then your ignition is going out.
Good luck and happy riding
Mike