Torch tips - Convert, Acetylene to Propane

I’m using a Little tourch with oxy/acetylene and get a pop just with
the #4 tip. It doesn’t matter if I turn fuel or oxygen off first.
One thing to note is, that this is the only tip I ever used on
oxy/propane. Never could get the smaller ones to light reliably and
for larger tips, I want the extra heat of acetylene. Haven’t used
the propane in a year or so. Does anyone know if switching back and
forth is harmfull to the tips? tx,