Cleaning the stem inside as well? I noticed when I pulled out the stem/bit itself instead of a filter there was a long 4-blade stick(?) instead of a filter. Covered in tar of course but strange. Thanks for the suggestion of everclear, I tried doing a search, but I couldn't find (well I don't think) the right product.
When I restore pipes I usually start by soaking the stem in a solution of water and bleach, roughly 75:25. After an hour in the bleach, I scrub the inside of the stem with a bristle-type pipe cleaner, then soak some more, and scrub again later.
Often, when you have a pipe with a metal "stinger" installed, it will be stuck in place, and difficult to remove. In that case you might need to try several different cleaners to dissolve the tar so you can pull the stinger out and clean inside the stem. I've used various chemicals in my attempts to free old stingers: WD-40, lacquer thinner, oven cleaner, methanol, ethanol, acetone, xylol and MEK (Methyl Ethyl Ketone) are the ones I've used in the past. I tend to try each one with just a few drops on a pipe cleaner at first, until I find one that seems to be capable of dissolving the tar buildup. I then use it to soak the stinger and the tenon, in a container with just enough of the liquid to reach the tenon. That avoids the possibility that the chemical might cause discoloration on the exterior surfaces of the stem. I use a simple glass graduated cylinder so I can see the liquid level. I put the stem in stinger downward, then use a syringe to add the solvent until the tenon is covered.
Oddly enough, bleach doesn't seem to discolor stems much. on the few stems that are affected at all, the discoloration is very shallow, and easily removed with very fine sandpaper and a quick polish.
Every smoker seems to have different thoughts on whether to leave stingers in place. Their purpose is to provide a surface where moisture can condense inside the pipe, so that the smoke is less moist by the time it reaches your mouth. I find that stingers tend to have tiny passages where the moisture condenses, partially blocking the passage of smoke, which causes the pipe to gurgle. The tiny passages where the gurgling occurs reduce the airflow and often result in constant relights. I prefer to smoke without the stingers.
On the other hand, I love all my pipes that use Dr Grabow style 6mm filters. The filters remove moisture well and never gurgle, and yet a pipe cleaner passes right through them easily. I've started modifying many of my estate pipes to accept Grabow filters, and I drill all my homemade pipes to use them.
