I worked in a Yamaha shop in 1973.
When new, the TX750 was a very nice motorcycle. We had a demonstrator, and I rode it alot. Smooth and torquey, with a very nice seat. I thought it was nice looking, too.
The 1973's did have a defect. The crankcase was porus in the area of the timing cavity, so oil would seep in & destroy the points. Yamaha had a recall on these, and were SWAPPING CASES on every one they could get back.
With this recall, their reputation was ruined. Yamaha had a tough time selling the 1974 TX750s, even though the defect was fixed.
I also heard that they would froth the oil in extended high-speed runs, and blow up. I've never seen one do this, but my sample was quite small.
Tom in Salem
I have found that all ugly things are made by those who strive to make something beautiful, and that all beautiful things are made by those who strive to make something useful. --Oscar Wilde