What should i look out for xt600

[otr002]

Well in our little part of the world the Australian defence force is auctioning off 90 odd XT600's fro 1991 with from as little as 8000k's up to 60000k's. the auction center that i'll be going to has 25 for sale with no reserve and no starting price. These are military bikes and have been serviced and repaired using only Yamaha parts, service intervals have been adhered to. the bikes are standard except for a large tank (acerbis) and additional wiring for black-out lights etc.
So the question are....

• what should i be looking for,
• do they have frame cracking issues,
• will they take a rebore
• are the parts expensive
• these don't have a kicker...good or bad..
• can the head be removed without taking the engine out of the frame

Any help would be great as this will be the dirt road bike, and my first foray into solo adventure touring, I'll be taking my riding buddy along and he intends to buy one as well

this is an example of the bikes...