If You start restoring an engine that has been partly dismantled for many years You might want to add some points in the beginning of Your "To Do List":
1) Evict small mouse living in crankcase.
2) Dismantle engine.
3) If mouse didn't clean up before leaving, remove all his/her belongings and food waste.
4) Continue restoration...
This Comet engine had been partly dismantled since the 60-ies. Cylinder in place but with magneto cover removed from the timing case.
Owner Hasse A recalls: "When I started to split the crankcase a full cup of sun flower seed left overs, drained out. I guess a small mouse must have chosen to live next to the flywheel with a bag of seeds conveniently nearby. Climb out, fetch seeds, climb back, eat, climb out, and so on.
Must have been a small bugger. The entry holes from the timing side into his flywheel abode are not exactly large.
And if the mouse was not black for a start, he certainly must have become so from living in an engine!