I recently bought an 89 xr600, test drove it it ran really good i thought but it was low geared and it came with a gang of extra parts so i swapped the front sprocket out for a 15 tooth vs the 14 that it had, the rear is a 45 so i left it. it has a 120/100-18 on the rear and a 90/90-21 on the front. the ride home was about 100 miles and from what i hear these bikes are pretty reliable so i had faith in it, got about 45 miles into it, stopped for gas topped of the oil, smoked a cig and let it cool down for a bit, got back on the road and about ten minutes later it started knocking and the motor seized while i was doing about 60-65 in friday getaway traffic. thank god i was able to keep it up and the car behind me moved into the next lane and hit his breaks so i could get over. anyways this is kind of my fault i forgot to ask the guy what the normal operating temp was. when i got off the road it was sitting around 250 which now i know is bad. i couldnt read the numbers while riding anyways it was pretty damn windy that night. so now im left with a 1300 dollar paperweight. im writing all of this cause i would like to know if anyone can help me figure out what happened why the motor overheated and what i need to look into replacing. the point of this was cheap reliable transportation and now its not pannin out that way oh well such is life. thanks in advance.