| Also known as | S692 |
| Diagram | Fig. 5 — CYLINDER BLOCK AND HEAD TR7RV · ref 5 |
| Subsystem | engine top |
| Listed in parts books | 1969–1974, 1976–1980, 1983, 1985 |
Cylinder base nut (12 point)
Triumph 12-point cylinder base nut, part 21-0692 (also S692), used to secure the cylinder barrel to the crankcase.
This is the 12-point cylinder base nut, Triumph part number 21-0692, also carried under the older S692 numbering. It shows up across a long run of cylinder block and head figures in the parts books, from the T90 and T100 singles and twins through the TR6R/TR6C, T120R, T140V, T140E, and TR7RV listings, which tells you it's a common piece of hardware across a wide span of engine years rather than something tied to one model.
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The base nut is what holds the cylinder barrel down onto the crankcase studs, and the 12-point head is there for wrench clearance and a cleaner look on the finished engine compared to a standard hex nut. Because it appears in so many different cylinder block and head figures, the physical nut itself has stayed a stable part across a good deal of the catalog's coverage.
If your parts book lists this as S692, that's the same nut under the earlier alias — no change in the part itself, just the older numbering convention. Given how often this one shows up across different figures, it's worth checking your own engine's cylinder base studs before ordering to make sure the thread and nut count match what you need.
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