I have a Crane toilet I installed new in 1985. It worked normally for many years. Then over the past year or so the flushing action slowed until it now requires two or three attempts to obtain a complete flush. I suspect that a clogged passageway to the siphon jet is not allowing water to enter the bowl fast enough to create a flush (I can achieve a complete flush on the first attempt by dumping a bucket of water directly into the bowl, so I know the bowl-to-sewer pipe passage is clear). I've inserted #14 gauge solid wire a couple of inches into each bowl rim rinse hole to check for clogs (e.g. mineral deposits) and found none. I've also done the same thing to the siphon jet hole at the bottom of the bowl....again no clog found there. I've snaked 1/8" flexible steel cable through each of the four largest rim rinse holes and through the large tank-to-bowl hole as far as I could push it....2 or 3 ft. depending on the particular hole......again with no obvious evidence of clogs.
I'm wondering if the internal passageway(s) leading to the siphon jet are clogged somewhere beyond the point (probably a sharp bend in the passageway) I can reach with the solid wire or the flexible cable. I'd like to fill all the passageways (both rim rinse and siphon jet) with calcium/lime/rust remover solution and let it sit for a day or so. Toward that end I've tried sealing the rim rinse holes with duct tape (after cleaning the rim) and plugging the siphon jet with plumber's putty. No dice.....the putty loosens almost right away and the tape does so after only a few minutes.....then the solution drains to the bottom of the bowl.
Anyone have any suggestions for adequately sealing the rinse and siphon holes so the chemical solution can have time to work?