I picked up a new Chacom Alize 815 that had been in the shop for several years, new old stock. The vulcanite stem had already begun to oxidize and the fit was quite loose. Worst of all the draw tasted like rubber tires. What's a fellow to do. I just smoked away, despite the bad taste, and eventually the taste disappeared and the stem tightened up too.
I've heard of similar experiences with rubber tasting vulcanite stems so maybe there is something that could be done, but it's all in the past now because my Chacom Alize 815 smokes now fabulously and with no rubbery taste.
I have purchased a St Claude recently, similar to dottiewarden's experienced, older pipe but unsmoked. The stem was oxidized, but that cleaned rather well with baking soda. The stem is very tight though, and still working on a solution around that. I think I have written a post on the subject a while back ..