Suggestions on getting off a stuck RD
 

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.

Bolt is seized, you can try and get some liquid wrench to penetrate, sit for a while and use a fresh allen key to try removal.

The other way is to heat the old derrailleur bolt up. But then you're risking the flame from the propane torch scorching the paint on the frame.

I'd go with operator's penetrating oil suggestion. Liberally applied to the area and allow to sit for a day. Another thing to do is use a pin punch and hammer to rap the derrailleur bolt a few times. Preferably one that fits down into the hex of the head. Then hit it like you would a good size nail a couple of times. Between the raps and the penetrating oil it should snap loose with the good fitting allen key without too much more effort.

The advice is much appreciated. I'll give the penetrating oil a try and see how it works. I can hit it with a pin a couple of times, too. Thanks again, I'll let you know how it goes.