My kid has a 2002 KX85 that was ridden and raced all of 2002,Not a problem.
Same for about 15 other kids that ride KX85's at our local club/track.
I do know that our Kawi guru (Tom Zont) has told me that he prefers to
never rebuild the kaw (65 - 85) cranks when the rod needed to be replaced
because they never were quite right afterwards, He has convinced me
to just do a new crank/rod assembly when the time comes.
You could call him at Great Escape Kawasaki for more info...