Originally Posted by fastbike

Thanks Dan, the mechanism is sufficiently different that an entirely novel technique is required.

Start by holding the axle in a vice with soft jaws.
Fit the first 4 parts to the axle ensuring #4 (inner spring cage) is rotated as far clockwise as possible so it engages the spring in #2 underneath.
Using some thin (less than 1.0mm) malleable copper wire bind the shift spring #5 to the outer cage #6 so this can be manipulated without it pinging apart. The shorter hook on this shift spring should be free (the longer hook latches into #6). This is a temporary arrangement and will be removed later so use only a simple loop and twist it with pliers to hold the two parts together.
While holding the lower hook of the spring with some fine needle nose pliers (ideally locking) drop this assembly onto the axle. It has tabs that fit into grooves in the axle so can go in one of 2 positions. Fit it so that the spring will be tensioned around 270 degrees in the next step.
As you slide the assembly down the axle, pull the lower hook of the spring around clockwise until it is past the notch in #4 and carefully latch it into place. You'll need a firm grip on the pliers if they're not locking as the spring hook will want to do its own thing. Press the outer cage #6 firmly onto the axle.
Remove the copper binding wire.
The next part is a little tricky as you need to manipulate part #4 clockwise while not upsetting the spring and plate you just fitted. Some small flat bladed screw drivers are useful but you need to end up tensioning the inner spring cage #4 against the spring in the shift cage #2 about 15 degrees so the drive key #8 will drop in after the next step. I used two screwdrivers, the first I used to manipulate #4 by poking it in the gap between the axle and #6 and levering part #4 around until I could get another screw driver , inserted from the side between the tab on #4 and the upstand on part #2. I then temporary fitted the drive key and using a shifting spanner rotated the key clockwise about 20 degrees until the the tab on part #4 moved past the upstand on part #2. I then wedged a small screwdriver to hold it in position for the next step and removed the drive key.
Fit the clutch onto the axle ensuring the slots at the perimeter fit over the tabs of the shift cage.
Now fit the drive key #8 - it should be rotated anti clockwise and fit down against the clutch with no gap. You may need to fettle around if the spring is not providing sufficient clearance against the axle to get it seated.
Remove screw drivers etc
Finally fit the tripper #9.