Sl-7402
 

I just pick up a very nice set of Dura Ace SL-7402 SIS downtube shifters for a vinatge bike project....one thing has me puzzled.....the left shifter or front derailer shifter is spring loaded....shifts fine to the larger chain ring but the srping action makes it return to the smaller chain ring. The Exage SIS I tokk off din't have this spring action. My question is.....how much do I have to crank down on screw piece that holds it on the boss to make it stay in position or am I missing something? I have cranked it down to the point that anymore and I will need pliers to make it tighter.

great shifters, i have them also, friction on front, indexed on the rear, for 2x8speeds
My tension is quite low and it remains in that position, and the screw can be tighten further by hand, but it's not necessary.

It sounds like you are missing a piece or they are assembled incorrectly. Look up your item here and it will be everything you need:
http://techdocs.shimano.com/techdocs/index.jsp

I took it off again and made sure there was no excess paint or anything on the boss......apparently the outer side of the shifter needs to set just right against the internal cylinder of the shifter......once it went back together......a few turns and it was acting the way it should........no need for excessive tightness. Thanks for everyones replies.