Hard to see the engine number, but here it is:

CX500 engine, 1980. After opening the engine case to borrow the oil pump, we found this:


Opening the back revealed an eaten plate:

An eaten crank plate, tensioner side:

Guide side:

Deeply gouged boss:

Below that, a slot had been cut:

Why the slot? At least two links were broken:


The chain was moving laterally as well, as evidenced by the polishing effect on the crank plate:




We pulled the gearbox to check it for metal particles:

There were plenty to be had across the gears:




If you’re intending on running an engine again which has had this sort of damage, the particles stuck to the gearbox cogs suggest it’s a good idea to remove it and clean it out thoroughly!