| Also known as | T1919 |
| Diagram | Fig. 8 — GEARBOX SHAFTS AND GEARS · ref 21 |
| Subsystem | gearbox |
| Listed in parts books | 1964–1965, 1967–1968, 1970–1971 |
Gearbox sprocket (20T)
20 tooth gearbox mainshaft sprocket for the four-speed Triumph 650 twin gearbox, drives the primary chain out of the box.
This is the gearbox sprocket, the 20 tooth splined sprocket that sits on the end of the mainshaft in the four-speed gearbox and carries the primary chain's drive out to the clutch. It's part of the gearbox shafts and gears assembly, and the catalog record ties it to Triumph 650 twins across a run of years from the mid '60s into the early '70s. You may also see this listed under its older T1919 form or the SPR-4SP20T tag, all the same physical part.
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The sprocket wears as the primary chain runs, and a worn or hooked tooth profile is one of the more common reasons a primary chain won't stay adjusted or run quiet. If you're replacing the primary chain it's worth pulling the clutch cover and taking a look at this sprocket while you're in there, since the two wear together.
We carry this under 57-1919 at the counter. If your parts book shows T1919 instead, it's the same sprocket - just call it out when you order so there's no mixup.
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