Earlier this week i adjusted the valves on my 08 crf250 and forgot to put the rubber gromet back on one of the valve cover bolts. Needless to say, after putting in 5 warm up laps on the track today, there was oil all over the outside of the motor. i immediately knew i had forgotten to put one of the gromets on. after confirming this was the case, i checked to see how much oil i had lost...there was barely, if any, showing up on the dipstick..my warm up session only lasted probably 12-15 minutes. i rigged up a piece of rubber to use as a gromet for the day and it worked great, filled the bike up with oil and never had a problem for the rest of the day. i am just concerned that maybe running it so low on oil for those 15 minutes or so may have caused some damage to the motor..i had to put about 400 ml of oil back in the crankcase to get it back to just about the top of the operating range..i always keep the recommended amount of oil in the bike...your input is much appreciated, i may be worrying about nothing.