does it have like a stuttering affect, like when you press the pedal it has a hickup and then goes? if so check the accelerator pump (that little rubber on the top of the carb) it might be perished. maybe you set the cable at a different position, thats why the pedal feels harder, or you did not put all the links back correctly, those carbs can be a mission sometimes. also check the accelerator pump itsself, it's got a plunger and that rubber at the bottom could be worn as well