Hi Friends Today I had a dramatic first run on my completly rebuild YZ 426. In last weeks I've instaled new piston, new cylinder, new timing chain and all bearings and seals. Why this run was dramatic? I starded my trip without any problems. No strange sounds, everything ok. After few minutes my engine seemed for me loud on clutch side but I was not sure. I was driving not so fast, not reving higher then half of the throttle. I found the clutch working strange and also I noticed strange noices. I decided to go home and check. Whole run was maybe 10-15 minutes. At home I found cluch cover to be hotter then usually, I've checed the oil and level was OK. I wanted to drain the oil to check the clutch but there was no oil in the sump!! I've took of the cluch cover, oil filter and there was only a little amoutn of oil. I took of the right side case with water pump and it appeared that I left some paper towel in oil line !!!! :-( Paper was wet and there was some oil in oil pump but not a lot. I've cleaned everything and filled bike with fresh oil. Started it without problems and had a short run first on low reves then higher. Engine is quiet , no strange noises and runs perfect. What do you think what shell I check to be sure that my engine is still like new after this stupid event? I'm planing to take a look under valves cover but shell I tear it down agian? I was running maybe 5 minutes with strange noises and probably negligible amout of oil, engine has not overheated- no water boiling.