| Also known as | E4539 |
| Diagram | Fig. 2 — CRANKCASE · ref 14 |
| Subsystem | engine bottom |
| Listed in parts books | 1964–1965, 1967–1968 |
CRANKCASE LEVEL PLUG - TRI 650 1963-68
Crankcase oilway/level plug for Triumph 650 twins (1963-68), threads into the timing-side crankcase over the oilway.
70-4539 is the crankcase level plug used on Triumph 650 twins, appearing in the catalog for the 1963-68 span under the CRANKCASE figure. It's a small threaded plug that sits in the timing-side crankcase, giving access to the oilway that runs between the scavenge pickup tube and the oil pump mounting face. Older parts books list this same piece as E4539, so if your book still shows the letter-prefix number, that's the same part.
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Because it threads into an oil passage, it's meant to be removed for cleaning that oilway out and then reinstalled with a fresh copper sealing washer. It's a cheap thing to have on hand if you're ever chasing an oil leak or doing a bottom-end clean-out on a 650.
We don't have a lot more written down on this one beyond the catalog listing, but the fitment and location are solid - it's specific to the 650 twin crankcase, not a generic bolt.
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