Also, swaping the main jet isn't going to fix the off-idle hesitation. You need to play with the pilot jet and fuel screw for that.
ALWAYS give your elevation when asking jetting questions.
As suggested, if not already done, remove the snorkle under the seat.
I've never known an XR400 that needed richer than 165/65 jetting at sea level, no matter how it was setup. If you're above sea level, you'll be leaner than that.
My intake and exhaust modded XR4 ran primo at 3600' with 155/55 jetting, so go from there to help in determining yours.