| Diagram | Fig. 5 — CYLINDER BLOCK AND HEAD TR7RV · ref 33 |
| Subsystem | engine top |
| Listed in parts books | 1974, 1976–1980, 1985 |
Bolt - rocker box
Flange bolt with a machined collar that secures the rocker box to the cylinder head on Triumph 750 twins, two per box.
This is the flange bolt that holds the rocker box down onto the cylinder head on Triumph's 750 twin. Two go on each rocker box, one on either side, for four total on the top end. It's a special bolt with a machined collar under the flange rather than a plain shoulder, so it's not a generic hardware-store substitute.
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Catalog listings for 21-2206 run across CYLINDER BLOCK AND HEAD figures for the T140V, T140E, and TR7RV, spanning appearances from the mid-70s into the mid-80s. If you're pulling a rocker box for a valve job or a top-end rebuild, this is the bolt you'll be reusing or replacing, and it's worth checking the collar and threads for wear before putting it back in.
Because it's a UNF thread with a specific length and a machined step under the head, grabbing a random bolt of similar size from a bin won't give you the same seating or clamping behavior. Best to match it against the original if you're unsure.
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