I was narrowly spared having to ride Yamaha's two-stroke engined TD1A, by riding something far worse, but I saw others struggle with them. John Buckner's father grew tired of the broken cranks, and carved a replacement out of 4140 steel, which he had lavishly stress-relieved and heat-treated. It broke while the engine was being warmed up in the pits.
The TD1B was vastly more reliable, and a bit faster, but its useful power band began at 9200 rpm, hit its peak at about 9800 rpm, and red-lined at 10,500. The engine would pull, after a fashion, from 8500 rpm but running it down there made the TD1B feel like a moped. Zinging the engine above redline meant you had cracked the wrist-pin bearing cages, and at some early point thereafter you could expect bits of cage and loose rollers to rain down into the crankcase. (This debris always tried to exit the engine through the transfer passages; you always had one tardy roller in a transfer window when the piston tried to close same.)
The extremely steep leading edge of the TD1B's power curve made it an exciting device for a novice to ride, as did the bike's short wheelbase and stiff suspension. It was the high-side champion of its time, and most novice-ridden examples had been crashed so much their fuel tanks looked like raisins.
Ah, those were the days...