i have a 02 660 that i bought from a buddy of mine that needed a new head put on it....got a head and installed and was getting everything buttoned up when i went to change the oil i pulled the plug on the crank case to find no oil in it....pulled the plug in the tank and it was full.....replaced both plugs and pulled the oil filter and it appeared to be new so i was thinking that the oil had been drained per it was torn down when i bought it....but then i got to thinking that the tank was full....so i refilled the tank and run it for a few seconds per the book and then pulled the drain on the crank case again to find that there was still very little if any oil there....pulled the line off next to the drainplug and oil came out....pulled the oil filter to find it still looked new and dry.....any ideas on what the problem might be....seemed to run fine without any noises for the few second i ran it but dont want to trash the motor with no oil...? any help would be of great value