ORIGINAL: Wild Foamy
sounds like its been left with castor oil/fuel in the crankcase, if its already mounted in a plane it may be easier to fuel it and start it up with an electric starter, then leave it running low-mid throttle range and give it a few revs, this should clear out the castor oil and get everything moving the way it should again. (worked for my old OS MAX 35)
NOT a good idea. Any congealed oil will not allow fuel, which contains fresh oil, to get to the bearings and other needed surfaces. You could damage bearings and score surfaces before proper lubrication has re-established.