A couple of years ago, my oldest raced the second loop of a Utah National Hare & Hound without any oil. The crank was being changed on his KX125, and it wasn't ready when time to leave, so I sent him ahead with friends with my KX250 and his KX125, less motor and tranny. The motor was finished by midnight, so I drove all night, slipped the motor in the frame while it was still dark, but forgot to check the tightness of the drain plug, AND forgot to wire the oil plug in place. Sometime during the first loop the plug came out, followed by the oil. After the race, we refilled with oil, and finished the National series with no problems. Imagine my delight at the end of the last event, and no tranny work!
The following year, the same thing happened to a friend with his KX250 (they now wire the oil plug as well), with no ill effects.
These KX's are made to take a licking and keep on ticking. The moral of the story, wire your oil plug in place!
Rick