just changed the oil on my 89 gsxr 750. It's been a long time since i've changed the oil.I had a lot of metallic slivers and a few pieces that looked like clutch material.I believe the oil i used was 10w40 as spec'd. What might this stuff be?The engine was rebuilt around 55,000 miles ago.I just changed to 15w40 now.Engine does not get hot and i don't rev the snot out of it.