I'm in the starting stages of putting together an engine to replace the very tired one that sits in my XR600. I picked up this 90 bottom end. It appears to have very low hours on it. There is very little sign of wear anywhere on any of the gears. It did suffer a bad piston seizure and completely toasted the cam and rocker arms. Looks liek a classic case of oil starvation. I just took the wrist pin out and removed the piston. The wrist pin didn't just slide out, but I did have to press pretty hard and work it back and forth. I did not have to resort to tools to remove it. Here is what I found in in the rod small end. It looks big in the photos, but it just lightly grabs a fingernail. A new wrist pin fits pretty well. So can I clean out the center and still run it? My first reaction is to replace it, but I wish to avoid splitting the cases if at all possible. Not that it matters all that much, but the engine will be in the stock configuration with 9:1 compression and the Honda cam. These are thumbnails. Click for a big version.