| Also known as | F13875 |
| Diagram | Fig. 22 — GAS TANKS · ref 21 |
| Subsystem | fuel |
| Listed in parts books | 1971–1974, 1976–1980 |
FUEL CAP GENUINE DOME TOP - 29-7898
Genuine dome-top twist-on fuel cap for Triumph gas tanks, PN 83-3875 (also 29-7898).
This is the genuine dome-top fuel cap, PN 83-3875, also cross-referenced under 29-7898. It's the twist-on style cap that seats into the filler neck on gas tanks across a long run of catalog appearances from 1971 to 1980, showing up in the GAS TANKS, GAS TANK AND TWINSEAT, and PETROL TANK figures. If your parts book still lists the older number 83-3875T, that's the same part under its prior factory designation.
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The cap is a push-and-turn design, meaning it locates into the neck and locks with a quarter twist rather than threading down like some earlier caps. It's a straightforward wear-and-tear item — gaskets dry out, the mechanism gets sloppy, or the old cap just doesn't seal right anymore. Because it's the dome-top genuine version, it carries the look factory tanks from this era used.
Our record doesn't spell out which specific tank neck dimensions or model years this exact cap requires versus other twist-on variants Triumph and BSA used over the decades, so if you're not sure your tank neck matches, give us a call before ordering and we'll sort out fitment with you.
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