| Diagram | Fig. 8 — GEARBOX SHAFTS, BEARINGS AND INNER COVER · ref 25 |
| Subsystem | gearbox |
| Listed in parts books | 1974 |
CAM PLATE-500 - Replaces 57-1458, 57-1768
Gearbox cam plate for Triumph 350/500 unit twins, replaces the earlier 57-1458 and 57-1768 numbers.
This is the gearbox cam plate for the Triumph 350 and 500 unit twins, part number 57-4218. It's the toothed steel plate that rotates on its spindle inside the gearbox and translates movement from the selector mechanism into the sliding motion that moves the selector forks and shifts gears. This number replaces the earlier 57-1458 and 57-1768 cam plates, so if your parts book lists either of those older numbers, this is the current part that fills that slot.
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The cam plate has to stay true and the grooves have to stay sharp for the gearbox to shift cleanly. If a cam plate is worn or warped it tends to bind against the selector forks, which shows up as vague or hard-to-find gears. Since we don't have detailed catalog history logged on this one beyond the supersession, give us a call if you want help confirming exactly which gearbox generation you're working on before ordering.
Worth handling as part of a full gearbox inspection rather than swapping in isolation - check the selector forks and the plunger/detent setup while you're in there, since wear on one often shows up as trouble on the others.
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