Originally Posted by
unworthy1
the flush with WD40 is the only fix you (or any mechanic) can really do. If you have a broken return spring, you can't buy the part and Shimano does not even recommend repair (they want you to buy a $$$ replacement brifter, go figure!).
Good news is the flush-out frequently works. You *can* do a little disassembly to help expose the innards for flushing, but yes, special tools (TL-ST01, TL-ST02) are required for both take-apart and reassembly, and it won't really help the cleaning that much.They recommend you re-grease one inner surface, but in reality if the WD40 works you can just go forward without new grease and prepare to use the WD40 again, when needed.
Actually my LBS ordered me a new Shimano return spring a couple months ago. You just need someone who knows how to read their parts book. If there is no physical damage dried prawl pivets are normally the problem as noted in several replies here. As a "flipper" I get a lot of practice working on these. Just applying a penetrant, (PB is the best), rarely works. Penetrant
and rocking the prawls with a pointed tool will eventually free them. It has never failed for me. On some models you may need to break away a piece of the plastic cover to get to the prawls. A small Allen wrench works well as the pointed tool. The same procedure works on "Rapid Fire" shifters.