I got a CLEAN 83 XR a couple months ago and have been going through it. I paid $180! After an air cleaner, seat cover, led taillight, front fender, oil/filter change, and going through the carbs and jetting for my altitude (5200ft) it still had a high RPM break up. Turns out that last night I was hitting a trail when the headlight flickered. I found a nasty female spade connector on the bulb. Replaced it and now there is no top end break up. There was evidence of melted insulation on the wire near the nasty connector...due to resistance. Just wanted to pass this on. I guess this is a total loss ignition system?...no battery. The arcing (or more likely an intermittent short at high vibes) that was going on at the headlight connection must have thrown things off. Hope this helps somebody. ---Will