You weren't clear in you original post but I now gather that you've identified the #4 cylinder as the one that's giving you the problem. Furthermore you have a new spark plug, at least in that cylinder, and compression is good. I hope the plug is correct for the bike. Finally this seems to be a problem at low RPM. It's OK at elevated RPMs.
How did you identify which cylinder was acting up?
It seems to me that there's a primary fuel delivery problem. I would have expected that swapping the primary injectors around would have caused the problem cylinder to move. You could also try swapping the primary and secondary injectors for that cylinder but swapping between cylinders sounds better. But if not, it points at the wiring. Measure the voltage at the Y/R lead to the #4 primary injector. Also remove the grey ECM connector and look for corrosion. Finally look for damage to the harness between the injector and the ECM.
Is your PAIR system still installed? How about the EXCV system?
How did you identify which cylinder was acting up?
It seems to me that there's a primary fuel delivery problem. I would have expected that swapping the primary injectors around would have caused the problem cylinder to move. You could also try swapping the primary and secondary injectors for that cylinder but swapping between cylinders sounds better. But if not, it points at the wiring. Measure the voltage at the Y/R lead to the #4 primary injector. Also remove the grey ECM connector and look for corrosion. Finally look for damage to the harness between the injector and the ECM.
Is your PAIR system still installed? How about the EXCV system?
