| Also known as | 23T, E12599 |
| Diagram | Fig. 5 — CYLINDER BLOCK AND HEAD TR7RV · ref 40 |
| Subsystem | engine top |
| Listed in parts books | 1971, 1974, 1976–1980, 1985 |
Rocker box gasket
A wire-reinforced paper gasket sealing the rocker box to the cylinder head on Triumph oil-in-frame twins.
This is the rocker box gasket, 71-2599, seated between the cylinder head and the rocker box on Triumph oil-in-frame twins. It shows up in the parts book figures for the cylinder block and head assembly across TR6R, TR6C, TR7RV, T140V, and T140E listings, so it's a fixture across that whole family of top ends. It's a thin wire-reinforced paper gasket, and its job is straightforward: keep the joint between the rocker box and the head oil-tight while the engine's running and heating up and cooling down over and over.
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The legacy alias here is 23T, and it also carries the E12599 form in some records - all the same physical part under different numbers depending on which parts book you're holding. Down the line this part number was superseded by 71-2599E, so if you're chasing this by an old book number and the counter comes back with the E suffix, that's the same gasket, just the updated designation.
Because it sits right at a joint that has to stay sealed under heat cycling, it's a part worth replacing any time the rocker box comes off, rather than trying to reuse the old one. Catalog appearances run from 1971 through 1985, so it's been in continuous use across that stretch of the oil-in-frame twins - confirm which head and rocker box setup you've got before ordering if you're not sure.
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