I know this has been discussed before, and I've done a lot of reading about this problem and some troubleshooting. I'm almost ready to throw the toilets out and buy new ones.
I've been in the house for over 1 year, and the two toilets on the main floor clog at least 50% of the time when flushing solids. When flushing only water, it's never a problem. Both toilets are Mansfield from about 1978. The tanks of both fill up to the dip tube, and there is nothing in the tank to use up space to save water. I've poured 1/2 gal of muriatic acid down the dip tube to clear out the water jets, which didn't seem to be clogged at all to begin with (I tried a piece of wire first). These toilets don't have the large water jet at the very bottom.
They're on a city sewer, and I don't notice any other odd symptoms like gurgling sinks. However, one of them is a little loose on the mount, but there's no water leaking. It's rare for the clog to occur inside the trap; it almost always clogs within view right at the drain hole entry. This makes me think there isn't anything stuck in the trap, although I haven't discounted this possibility.
Any ideas before I throw them out?!