i believe they had an issue with the anti-freeze hose leaking or rubbed against something and wore through,i have talked to a few ppl before i bought one like that plus my bro has the 700 and he had the anti-freeze hose isssue...decent price check the CV joints,boots and air box.
I used to own one of those... great machine. I didn't have any problems with it.... I put on 4000 miles, and then had to put in new rings on the pistons. I didn't have any issues with the antifreeze leaking, just had the odd CV boot to replace and the drive/prop shafts started to get sloppy because of the wear. I have nothing bad to say about this machine.
One thing you might consider is getting a good dealer to check it out, they can tell you EVERYTHING that is wearing out on it. It usually costs about $100 depending on how indepth you want to go, but IMO it is money well spent. If the quad does check out ok i would say the price good.
The wife has an 03 only put $1,500.00 into it last year because I couldn't sell it. That said I beat the Chit out of it when I had my sport quad because it rode soo nice, like pillows under your a#$.