Thanks for the replys.
It makes no differencewhen you remove the spray regulator.
When you remove the tip, the head 51-071, threads on completely and touches the body. With the spray tip is in place, the spray head comes up about 2 threads short of seating. I am not sure if the spray tip taper should seat down into the body past the taper and over the flat area of the spray tip. There is absolutely nothing to interfere with the tiup seating.
I am wondering if for some reason the spray tip needs to be "pressed" down into the spray body? When you remove 51-071, the spray tip 41-004 is loose and falls out immediately. It looks to me like the spray tip should seat down into the body and the male taper should mate to a female taper in the body.
tho9900 - is your spray tip "stuck" to the airbrush body? As soon as I disassemble mine falls loose.