I have a 85 Nishiki Prestige, with the original SunTour Cyclone RD still on it. I wanted to take it off to put on a newer indexed Shimano 105 RD, but I can't get the RD bolt to turn. Any recommendations on getting the RD off? There is no damage to the frame or RD that I can see, everything looks fine, in-line and true. I think its mostly a case of a bike that sat around a while.