BTW, when you install the new parts, look very carefully at the rod-to-wristpin and the wristpin-to-piston fits. The grainy looking pockmarks in the piston wall often happens from too lean running. And that can wreck the wristpin fits.

BTW, it is a fact of life with 100% castor fuel, that varnish buildup can bite you someday. It makes the needle setting you've learned to trust a bit of a risk. The buildup will eventually cause a problem. The needle gets overly sensitive as one symptom. Usually is the first symptom. Engine goes lean "for no reason" is another. It doesn't go real lean to begin with, but does give you pause if you're paying attention.