Don't turn the engine by the fan. Turn it directly from the crank.
If the crank has already moved, whatever is done has been done. Just fog it up, fill up the crankcase with fresh oil and spin it a few rotations without spark plugs to wet the upper end. Keep the carb dry during this step. If the carb has been sitting, you may need to rebuild it first. Ideally, you want to check compression to make sure you don't have a serious problem. Once you're comfortable that it's rotating freely, and the compression is not indicating a major chamber leak, button it up and give it a try. Don't fret if it won't start. After two decades, getting spark and fuel going is not always an immediate result.
If you're not sure about these things, have a mechanic friend on hand when you do this.
