Recently I was put in charge of freeing up two OS engines that were siezed from sitting, it turned out a little heat will get the castor to change from "varnish" to Molasis. I had to let the motor soak in hot oil then turn it over to suspend/disolve the old castor oil. Hope this will work for you. Using just heat will work but the castor will just reharden as the parts cool.Calvi.