ORIGINAL: Fuelman
If you still have a decent pinch and the piston/sleeve/rod look and feel in good shape and the bearings are not shot, then run it!
just seeing that the engine has had a life with plenty of castor oil tells me that it may be in better condition mechanically than is appears to be visualy.
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Ditto what Fuelman said.
It might not hurt to give it an antifreeze bath. Once the grime is gone, it is much easier to be objective about the engine's state of health.
Ed Cregger