Hi Jerry,
I don't have a pump but I am poking a coat hanger in there a few times a day. I have the tip bent so that I can make it go around the 6th cylinder and I use it to scrape at things. Hopefully that will help. I've thought about looking for a bottle brush I could braze to the coat hanger but haven't seen one I think is stiff enough yet. I need to go to the Chinese Market. There are tons of brushes there. Thought of using a gun cleaning brush but those are not cheap and it definitely would not turn a corner. Besides most of those are brass and aluminum and CLR warns you not to use the product on copper, brass or aluminum. I took one of the larger pieces of what first washed out, put it into an old film canister (nylon) and after about 4 days the CLR reduced what was about the size of a small pea to a gritty dirt-like slurry which will drain out easily. I'm not thinking all of it will come out, but I'm confident a lot will. Once it is back together I'm happy to try your acid treatment or possibly oxalic acid.
Jon
