| Also known as | E7563 |
| Diagram | Fig. 4 — MANIFOLD AND TAPPETS · ref 23 |
| Subsystem | engine top |
| Listed in parts books | 1968–1971, 1974, 1976–1980, 1983, 1985 |
'O' ring
Tappet guide block O-ring for Triumph twins, seals the tappet block against the cylinder to keep oil in.
70-7563 is the O-ring used on the tappet guide blocks, sitting up in the cylinder block and head area right around the manifold and tappets. It seals the guide block so oil doesn't seep out where it meets the cylinder, which is one of those small parts that causes an outsized mess if it goes hard and starts leaking.
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This one shows up across a wide swath of the parts books, from tappet block figures on 500 twins like the T90 and T100 variants through to later twin-carb and single-carb head arrangements, with catalog appearances running from 1968 into the mid-80s. It was previously listed under 70-8782 before the factory renumbered it to 70-7563, so if your parts book or an old parts bag says 70-8782, that's the same O-ring.
It also carries the E7563 alias, which you may run into on older documentation. Given how many head and tappet configurations this part turns up in, worth checking your own figure against the parts book before ordering if you're not sure which guide block setup you've got.
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