Over 5 years since the last post. I'm happy to say that in that time the ZR 600 is still going strong - 1500 miles plus on that engine! Only issue was a hose leak at the oil pump. I swapped that out, no issue since with the engine.
But, the chassis, that's another story, all the shocks need a rebuild. At this point I don't think I am going to do it, we're in the market for a 2-up sled so I think I will either sell ZR outright, or trade it in towards another sled.