A 'roadside' repair is possible
 
A broken spring could be repaired out on the road. Lean the bike over to keep oil in gearbox. Biggest problem is access past the support tube to bottom Allen screws. (1,400 miles.)
 

   


Tools easily carried. If no spare spring: grips needed to bend broken spring.
Filed the edges off, cut the short end shorter, to get at lower cover screws.
Leaned over to save oil in box. It should be a bit more but garage too narrow.
Oil saved in leant-over box. There was a lot of metallic filings in oil again.
This is the 'boss' that spring coil is located on.
This is the repaired broken spring on re-profiled shift plate. It worked fine.
Short, repaired spring seated in re-shaped plate corner.
Repaired spring bend.
Repaired spring on repaired, filed-down ratchet arm boss.
Fit new parts when home, or carry spares, or a file to fix big boss on the road.
A new spring on my re-shaped plate: it doesn't seat in the corner.
View of all the spring contact points.
A bit more work was done to better accommodate the new, full-size spring.
Repared broken spring beside a new spring.
Repaired spring and new spring.
I am confident that the repaired spring would have continued to work fine.
Shorter, repaired spring.
Full size spring.
New spring and new, correct size boss.
The old boss that I think caused the failure: it's over 16mm diameter.
The new boss at correct 15mm diameter and old boss repaired by filing down.
The three gearbox selector springs.
 
I rounded the edge of this arm too,to give a better seat, 'just in case'.
Back together and ready to replace.