Does anyone know if it's possible to take the cog off of a Shimano 3cc 3-speed hub without risking opening the hub? I've read that they are a pain to repair and the one I have works fine, so I don't want to mess anything up. I would like to clean up the cog since it's covered in 20 years worth of grime and it would be easier to take it off the hub and scrub it off in a sink. Thank you!