The pilot will not lite on a robertshaw 7200ercs uses L.P. gas I have use this furnace for the past 5 years and I have lite the pilot before and I followed the instructions . I held the valve in he set position for a minute to bleed off any air that may be in the line but it still will not lite I can smell gas when I hold the pilot knob in the set position To lite the pilot so I know gas is flowing out of the pilot tube

The pilot light orifice could have a restriction. On LP gas it is a very small orifice to start with. Usually you have to take the pilot apart to get to the orifice. On many pilots the orifice is located inside the pilot housing inside where the 1/4 inch aluminum screws into. When removing the aluminum tube be very careful as the brass nut has a tendency to corrode to the steel pilot base. I suggest you spray a little WD-40 on the area before trying to disassemble the aluminum tube. When you find the orifice it is possible to see a spider web in the area or the pilot hole will be restricted with dirt/debris.

What ever you do leave the pilot hole the same sizes do not ream it out or you will have a 6 inch pilot light sooner than you think. With propane gas it does not take much to damage the orifice.

Hopefully this should fix the problem. Since you are taking it apart you might as well install a new thermocouple while you are at it also.

Becareful when messing with LP/Propane