| Diagram | Fig. 5 — GEAR CLUSTER · ref 113 |
| Listed in parts books | 1969–1971 |
BSA Selector fork, mainshaft
Selector fork for the mainshaft in the gearbox, shifts gears into engagement as part of the gearchange mechanism.
57-3854 is a selector fork off the mainshaft in the gearbox, the piece that rides in a groove on the gear cluster and gets pushed back and forth by the selector mechanism to slide gears into engagement. It shows up in the parts book under gear cluster and gearchange mechanism figures, so it's tied directly to how the box shifts between ratios rather than to the outer cover or the pedal linkage itself.
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Our catalog record on this one only spans a couple of model years in the late '60s/early '70s and a handful of listing rows, so there isn't a lot of extra detail to pass along beyond what the fork does and where it lives. If you're pulling the gearbox apart and need to know which fork this is versus the layshaft fork, have the parts book open to your model's gearchange mechanism figure to confirm it's the right one before you order.
Given the description names it as a mainshaft fork specifically, don't swap it with a layshaft selector fork even if they look similar sitting on the bench - they ride in different grooves and won't shift the right gear if you get them crossed up.
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