The drive chain conversion job was neat. I only remember the one but didn't follow racing very closely. People all said it was for more power to the wheel, but I always thought it was for adjustable final drive ratio.
I had a friend who went thru two, both from new, he did mega miles. Each was traded with 250-300 K km covered. They still ran well and I don't think he ever did more than regular service to them. Je lamented the end of the model but traded the second on the xs replacement .