| Also known as | E8782 |
| Diagram | Fig. 2 — CRANKCASE · ref 33 |
| Subsystem | engine bottom |
| Listed in parts books | 1969–1974, 1976–1980, 1983, 1985 |
O-RING INSPECT PLUG
O-ring for the inspection plugs used on unit Triumph engine and gearbox covers, current number 70-7563.
70-8782 is a small O-ring used under inspection caps and plugs on the unit-construction Triumph twins. It shows up across a wide spread of engine and gearbox areas in the parts books - crankcase, cylinder head, rocker boxes, gearbox covers, and both inner and outer chaincase covers - because these bikes use the same style of threaded inspection plug in several places, and each one seals with an O-ring like this.
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The part appears under a huge number of catalog listings spanning 1969 through 1985, which tells you it was a long-running, widely used seal rather than something specific to one assembly. Later parts books list it under 70-7563 as the current factory number, so if your book shows either number you are looking at the same seal.
It is a cheap part to keep on hand. Given how many spots on these engines use an inspection plug, it is worth having a few spares in a drawer before you go pulling covers - a torn or hardened O-ring here is an easy way to get an oil leak or a chain oil feed that will not hold pressure.
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