I had 9 inch baffles i cut down to 3 1/2 inches in my 2008 1200 nightster, will i have any problems ?

Question

they were slip-ons so it didnt effect the 02 sensor

Answer 1

I doubt it would be much of a problem. The backpressure and restriction would come mainly from the size of the outlet hole. I would put in a fresh set of plugs and check them so see if it was running too lean though. There are other signs with an EFI bike too, like surging at low RPMs and a lot of popping on deceleration.

I wish HD would just solve it for everyone and put in a wide band O2 sensor and just make it easy on everybody.  

Answer 2

probably not. The EFI system is computor operated and can self adjust up to 20% richer or leaner without needing to have a new download. Cutting the baffles will tend to make it run slightly leaner, but well within parameters. If you feel a difference in performance, more loud popping, surging or excessive heat off the motor when sitting at a light, you may need to make some changes.