I have a parts bike I bought a 1973 cd175, the engine had the top end taken apart down to the pistons when I bought it. The engine is in really nice condition, so I have decided to rebuild it for a spare. The engine turned freely by hand, but once in a while it would just stop turning for some reason. I have both side covers removed,and the pistons off. Then looking into the bottom of the case with a trouble light, I see this thing coming through the hole in the bottom side of the case from the rotor side. First off I thought it was a small thread tap, so I get a magnt, and work the piece out of the hole on the opposite side of the case, below the oil filter. I have looked through the clymer manual. but don't see anything that looks like it. Can anyone identify this part, thanks.