| Diagram | Fig. 34 — SPEEDOMETER AND TACHOMETER · ref 10 |
| Subsystem | electrical |
| Listed in parts books | 1976–1978, 1980, 1983 |
| Also fits (as replacement) | 1979, 1985 · for 71-4136 |
TACH DRIVE BOX 1969-ON,650/750 TRI
Tach drive gearbox for 650/750 Triumph twins, 1969-on, also known under the older factory numbers 70-9331 and 71-4136.
This is the tach drive gearbox, the small housing that takes rotation off the engine and sends it up the cable to the tachometer. Catalog records tag it for 650/750 Triumph twins from 1969 onward, and it carries forward under this number from two earlier factory part numbers, so if your parts book or an old invoice shows 70-9331 or 71-4136, that's the same physical piece.
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On the bike this is the connection point at the end of the tach cable, down at the drive gear that's turned by the engine. If your tach has stopped registering or bounces around, this gearbox and its drive gear are one of the first things worth checking, along with the cable itself.
We don't have more detail on this one beyond what's above. Confirm the fitment against your engine and cable setup before you order, since the catalog note covers a broad span of twins rather than a single model year.
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