| Also known as | W103 |
| Diagram | Fig. 23 — AMAL CARBURETTER, TYPE 376 · ref 46 |
| Subsystem | engine bottom |
| Listed in parts books | 1960–1968 |
NUT 1/4 CEI REDUCED HEX
A 1/4 inch CEI reduced-hex nut (37-0103, formerly W103) used at inlet manifold, oil pump, and gearbox cover fastening points on Triumph twins.
This is a small reduced-hex nut in 1/4 inch CEI thread, 37-0103, listed in the old books as W103. It's a common fastener in the pre-unit and early unit twin lineup, showing up wherever a low-profile nut is needed for clearance - inlet manifold studs, oil pump and release valve assemblies, gearbox outer cover fasteners, and around the carburetor mounting hardware on single and twin carb setups.
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The reduced hex head is the whole point of this nut - it lets it tuck into tight spots on the manifold or pump housing where a standard hex nut would foul on a casting or another fastener. It shows up over and over in the parts books across a wide span of figures because Triumph used this exact fastener in a lot of small places rather than switching sizes.
If you're chasing down one of these because a manifold nut walked off or stripped, this is the one to grab. It's not model-specific in the way a big casting is, so don't assume it's exclusive to one machine - check your own parts book figure to confirm it's the nut called for in your spot before ordering a batch.
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