HIGGINS!? 

I just picked up a bianchi sport sx(86-87). Its been sitting in storage on a hanger for god knows how long. I'm having an issue with the chain tension, i can pedal forward but as soon as i coast or backpedal the chain loosens and i have to spin really fast to get the chain re-tensioned. I am also able to backpedal and the tires spin and when i walk the bike the cranks spin(like a fixed gear) I was able to get it working somehow for about 4 minutes, so i don't think its a chain length problem, then when i took it back out to test ride it gave me the same trouble.

rickowensis

Your rear hub is not freewheeling causing it to behave like a fixed gear. The grease in the rear hub has become stiff which prevents the pawls inside the freehub from releasing.

If you have a freewheel, you can spray lubricant into the gap on said freewheel which will free up the pawls. It's easiest to do this if you remove the freewheel first.

If you have a freehub, spray a little degreaser into the backside of the hub to free it up. The degreaser will liquefy the old stiff grease, allowing the pawls to move freely.

This is relatively commom in bikes which haven't been used for a while. Good luck.

HIGGINS!? 

thanks

tellyho

I'd add to the WD 40 trick (I wouldn't use degreaser) - follow with some Triflow. You want to loosen it up, and for it to stay loose.