I would assume that you are referring to the '97 ZR580 efi and the '98 ZR600 efi problem - that is the only "high rate" failure of an AC stator - there have been some limited problems on some of the other models, but not any higher than any other brand, model, etc.
I had a zl 550 esr. bought it new and sold it with 2500 miles. the only problem I had was the starting motor which was a problem on all arctic cats that year and the next couple. had to replace them every few years or use them infrequently. I was my least favorite arctic cat but that could be because of my riding style. It does 100 per on the speedo in perfect conditions on the lake I would say 10 mph less on radar. its not as powerful as the 500 from the same era (80 hp vs 96). it is almost as fast top end but not as quick. It doesn't have efi which is an option I liked on my ac's. it is not as good in the snow as the firecat chasis. It is cushy on the trial or lake if not riding aggressively. Stutter bumps at high speeds or ditch banging is not recommended. If you hit it hard enough it will rebound and jolt your spine. I couldn't hit my firecat hard enough to do that. the cg is higher than the zr's(the old 96 zr would do a 720 before you rolled it) and the firecats and as a result it is a little tippier. It is still a fairly stable machine though. I have operated in all kinds of conditions and run it agaisnt all kinds of sleds if you have any specific questions.
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