Reassembling Shimano Dura-Ace 9-Speed STI Levers

Reassembly is the reverse of the strip down but, since several springs need to be re-engaged and tensioned, it's the more difficult procedure.

Thoroughly degrease, clean and dry off all parts. Inspect for signs of damage although, as previously noted, your options are limited as to replacement parts.

All moving parts need to be greased for reassembly. Most parts should be lightly greased but more liberal application is appropriate for sliding contact areas, e.g. ratchets and pawls. If you're particularly loyal to Shimano, their Dura-Ace grease is a good choice. Otherwise a light general purpose grease, such as wheel bearing grease from your local auto store, is ideal. Avoid lithium, copper and graphited greases as these can clog the mechanism.

Mount the spindle in a vice by an M4 bolt threaded into the front. Slide the Flightdeck sensor onto the spindle followed by it's copper spacer (if present).
Engage the ratchet bush with the spring in the ratchet drum and press the bush into the base of the drum. The spline will allow the drum to be located in two opposing positions. Orientate so as to place the cable guide at the top. Slide the drum and bush onto the spindle. Use a suitable spacer to prevent the drum engaging with the Flightdeck sensor at this point.
Slide the cage onto the spindle. Rotate the drum against it's spring to bring the ratchet into line with the pawls and press the cage into the drum. The drum will need to rotate about one quarter turn in the direction of operation - clockwise for right lever anti-clockwise for left lever. Remove the spacer below the drum and engage with the tabs on the Flightdeck sensor.
Assemble the shift mechnism into the outer lever and adjust the bearings. You'll need a thin 9mm across flats spanner such as the cone adjusting wrench supplied with retail Dura-ace levers. Avoid getting grease in the thread in the front of the spindle as this will interfere with the thread locking compound.
Mount the spindle in a vice again. Install the outer pawl and spring in the lever to engage with the ratchet drum. Verify that the pawl slides freely in it's slot. Avoid getting grease in the screw hole for the inner lever retaining plate as this will interfere with the thread locking compound.
On the triple shifter, place the 'mickey mouse' washer over the pawl cage. Note alignment over pawl pivots.
Slide the release plate onto the spindle followed by it's bush. The right-hand shifter has a plain bush, the left-hand has a stepped bush that also serves as a spacer and should be installed with the step and it's longer side to the rear of the release plate. Engage release plate tracks or pegs with the pawls in the mechanism. Slide the inner lever return spring onto it's pivot. Slide the lower plate for the inner lever onto the pivot. This plate retains the outer pawl in it's slot. Slide the inner lever onto it's pivot and hook it's return spring to locate on the lever. Engage with the inner lever with the release plate. Place the outer plate (or plates) over the spindle and inner lever pivot and retain with the cross-head screw. Use thread locking compound on this screw.
The left shifter has two outer plates, a small one that covers just the inner lever pivot and a larger one that covers the release plate as well. Note that the the release plate bush spaces the outer plate away from the release plate so that the release plate spring can run between them.
Place the dust cover over the adapter plate and slide the adapter plate onto the spindle. It can be useful to fix the dust cover in place by applying a little silicon sealant between the dust seal and the adapter (be sure to clean any oil & grease away first). The objective is to hold the dust cover forward, against the back of the shifter. Engage the release plate spring. Left-hand lever: the shorter tang hooks into the release plate, the longer tang into the adapter. Right-hand lever: the spring is located entirely on the adapter. A projection from the rear of the release plate engages in a loop of the spring through an aperture at the top of the adapter. Slide locking washer onto spindle, raised tabs uppermost. Apply thread locking compund to the spindle thread and fit the retaining nut. Requires Shimano special tool TL-01.
Remove lever from vice. Lightly grease the main lever return spring and fit it into the outer support cap (front cap). It locates in a small hole. Fit the front cap support bush (the square one) and washer (if present) to the front of the spindle. Hold it in place with a little grease. Press the return spring into the front cap to hold it in place and give some initial tension then locate the spring in the hole in the front plate of the main lever assembly and pull it round around until the front cap aligns with lever body. The cap extends back over the full length of the shifter and engages with slots in the adapter at the rear. Secure front cap with screw and star washer. Use thread locking compound and, because the thread in the shifter axle is sure to be oily by now, clean threads with a rag soaked in solvent beforehand.
Fit top cover and secure with screw. You may want to leave the screw loose on non-triple levers since you will need to remove the cover again to fit the gear cable. Or indeed, you could cut a small hole in the cover so that the cable can be fed through without removing it. The Flight-Deck sensor cable goes under the cover. On triple levers, there is a projection on the front cap which the cable goes above so that it is held away from the shift drum. Then the cable runs down the side (inside when on the bike) of the adapter and through the hole at the base of the handlebar bracket. Fit Dura Ace nameplate.
Fit plastic bushes to ends of brake cable hook and press into it's slots on the adapter. Align the narrow groove in the brake pivot axle with the grub screw position in the handlebar bracket. Fit the brake lever return spring over the sleeve in the adapter and hook into it's hole in the side of the adapter. Slide the handlebar bracket over the shifter adapter, with the return spring pressing against the handlebar bracket. Shimano offer a special tool for locating the spring but an offcut of gear cable outer works just as well. Press the axle through handlebar bracket and shifter adapter.
Lock pivot axle in place with grub screw. Use thread locking compound. The grub screw doesn't tighten against the axle and only needs to be inserted flush to engage with the groove. If the axle comes out you won't have a brake, so get this right. For reasons that aren't entirely obvious, this grub screw can be difficult to remove after the lever has been in use for some time so be sure to use a good Allen key of the proper size (2mm) to avoid rounding out the socket and give yourself the best chance of getting it out again. Fold the Flightdeck cable and position the connector inside it's housing. Replace the cover. Fit the rubber hood.