Originally Posted by
gaucho777
It would be helpful to know what exactly happens in the 9/10 times when it doesn't work. The lever moves, but not the front derailleur? Does the cable go slack? If that's the case, it could be a problem with the Front derailleur (for instance, damaged tension spring).
Sorry, my mistake. I read 7400 and assumed downtube shifters. Disregard my advice for STIs. Chances are you have old grease gunking up the innards. I have very little experience with brifters, but I did bring one back from the dead by flushing with, then soaking in, WD-40 as suggested above, followed by some light oil. If that fails, this photo essay may be of help (though it's for a 600 STI overhaul):
http://imgur.com/a/0tPBK
Or you can contact Jim McVey for repairs (the SC guy suggested by Robbie Tunes):
reajcorp2@aol.com
http://www.facebook.com/home.php#/gr...d=100856572916
https://www.facebook.com/pages/Shima...r/137062087082