Classic & Vintage - repair retrofriction shifters?

Is it possible to repair simplex retrofriction shifters? I have several pairs of these and love them. However, I have a left shifter that isn't working as it should. I have heard that the internal spring breaks sometimes? Any suggestions? Thank you in advance!

I am not even sure what a Simplex retrofriction shifter is. Perhaps a picture for those of us who are less informed.

This is the later version.

http://gallery.me.com/justinhughes/100530/IMG_5478/web.jpg?ver=13254561660001

Andy, what do you mean by "not working as it should"? Is it just not holding properly? Check to make sure all of the parts are present.

http://2.bp.blogspot.com/_IJWmejgFtpE/TThPtORkZ7I/AAAAAAAAACY/UNerCHDONDc/s1600/simplex-retrofriction-components3.jpg

I'd also start with a thorough cleaning, as I've heard that dirt is often the culprit in these not "working right". I've never had mine go bad so never had to replace a spring, but as long as you can locate a replacement (good luck) or somebody could wind you one to match the old, no reason why it can't be replaced.

The springs are unobtainium. It shouldn't be difficult to figure out if that is the problem. You may have to buy another shifter to get the part if it is broken. Somebody posted here once that he has broken a bunch of them, but I found that hard to believe. I have one spare, but you'd have to pry it from my cold, dead hand.

I haven't tried to remove the spring yet, but all the other parts are there, and it is nice and clean. I'm using the model that fits to the campy shifter braze-on boss. I will dig deeper and see what I can find. Basically, there is no spring assist on the left lever one feels with retrofriction shifters. Thank you for the photos and guidance.

It is hard to describe the advantage of retrofriction shifters. With most friction shifters the effort it takes to pull or push the shifter is related to the tightness of the adjustment screw. On retrofriction shifters there is a spring inside the shifter that allows less "tension" on the adjustment screw lowering one's efforts on the downshift (rear derrailleur) making for smoother shifting with less trimming, but offers increased resistance on the upshift. For the front der. pulling back to shift to the big ring is easier than pushing it forward to the small ring. The shift levers counter balance the springs in the derrailleurs to some degree. Retrofriction shifters also reduce or eliminate the amount of autoshifting that occurs on some bikes. I have been using them for a long time (25+ years) and recommend them.