Servicing Shimano STI Levers

Ever wondered what's inside your STI levers? Here's a detail view of the guts of a Dura-Ace shifter:

There is a forbidden air around Shimano STIs. When asked for advice on reassembling an Ultegra STI lever, a Shimano spokesman said No one is going to be able to repair that shifter. He has disassembled a unit that is fabricated in Osaka using the very best of our SARA robots. (Shimano Automated Robotic Assembly).
In fact STIs come apart and go back together quite easily; if you can replace a head gasket on a Norton Commando, you'll be able to rebuild an STI. The real problem lies in the non-availability of spares. Which is really, really miserable of Shimano, especially when you see the spares list for something relatively mundane like a pedal. Hey, ho. If an internal component is broken or badly worn the only option is to canabalise another lever for parts. Don't throw that low mileage crash damaged lever away, get it touch and we'll buy it.

Shimano Warranty

Before you attempt to service your STI levers, consider this:
Shimano offer a three year warranty on Dura-Ace components, two years on Ultegra, 105 and the rest. At the first sign of shifting problems, if your STI levers are still within the warranty period, send them back to Shimano. Obviously you need to ensure that your cables are in good condition and the derailleurs move freely. But, if you isolate the problem by disconnecting the cables and the shifter still doesn't change up and down cleanly, there's a fault inside. Warranties take about a month to process and, obviously, exclude mis-use and crash damage. If you read the section below on shifter operation and faults you'll see some typical problems that occur.
Important: your warranty may be invalidated if you dismantle your levers.

If your STI shifter is out of warranty then you've nothing to lose. If you don't relish the task yourself, get in touch.
If Shimano refuse your warranty claim, we can provide a report on the condition of the lever that may assist your case. Although, in fairness, it has to be said that Shimano usually accept faulty STIs without argument; maybe they know there's a problem.