| Diagram | Fig. 3 — CYLINDER BARREL, EXHAUST PIPES, VALVES · ref 3 |
| Subsystem | engine top |
| Listed in parts books | 1970–1972 |
BSA Valve spring — inner
Inner valve spring for the A65 cylinder head, part of the dual valve spring set, PN 71-1177.
This is the inner valve spring for the cylinder head, catalog number 71-1177. It's one half of the dual-spring setup used at each valve, working alongside the outer spring to keep the valve seated and under control through the full range of engine speeds.
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The part shows up in the parts-book figures covering the cylinder barrel, exhaust pipes, and valve gear, and the catalog listings for this number run from 1970 to 1972. A grounding reference we found ties this spring to the A65 engine family, which lines up with the BSA manufacturer tag on this part rather than Triumph.
When you're pulling a head down for a valve job these inner and outer springs generally get replaced as a set since they're a wear item, not something to reuse indefinitely. If you're not sure which engine you're working on, check the number against your parts book before ordering, since valve springs are specific to the head they were designed for.
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