| Also known as | T2056 |
| Diagram | Fig. 11 — CHAINCASE AND CHAINS · ref 35 |
| Subsystem | primary |
| Listed in parts books | 1966–1970, 1974 |
TAB WASHER,500 C/S LOCK
Tab washer for locking the 500 gearbox sprocket nut in the chaincase, PN 57-2056.
This is the tab washer that locks the gearbox mainshaft sprocket nut in place, part number 57-2056, also seen in older books as T2056. It lives in the chaincase area, on the high gear/sprocket assembly, and its job is simple: once the sprocket lock nut is tightened down, the tabs on this washer bend over to keep the nut from working loose.
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The catalog lists it for the 500 class of unit-construction Triumph twins, appearing in chaincase and chain figures across a run of years from the mid-60s into the mid-70s. It's a small, inexpensive part that's easy to overlook, but if the tabs are already bent up or cracked from a previous removal, it's worth putting in a new one rather than reusing a tired washer.
Since it's specific to the 500 sprocket lock nut, check what you're pulling off the mainshaft before ordering to make sure this is the washer your gearbox actually takes.
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