[Gunngee]

The heat riser mounts on the muffler side are supposed to be like you described. However, if the actual heat risers are missing from the intake I would definately recomend getting an intake with them intact. These ones should not be welded though. It isn't meant to circulate the actual exhaust through the heat riser, where it mounts to the muffler is just meant to heat up the air inside the heat riser and well as the name says heat rises and boom. Your carb or intake might not be icing up but if it is cold then the fuel doesn't have a chance to vaporize and well liquid gas doesn't burn.
Personally I would just do what I did. Save up some money and buy dual kadrons. I never had another problem after that!