| Diagram | Fig. 16 — CARBURETTOR · ref 9 |
| Subsystem | fuel |
| Listed in parts books | 1960–1968, 1970–1974 |
Main jet (99-0446) (190)
Amal 190 main jet (376/100, 99-0446) for Monobloc and Concentric carburetors used on Triumph twins.
This is an Amal main jet, part number 376/100, cross-referenced in the parts books as 99-0446 and sized 190. It's the jet that meters fuel at higher throttle openings in an Amal carburetor - once the slide comes up past roughly a quarter to half throttle, the main jet takes over from the pilot circuit and controls how much fuel mixes with the air coming through the venturi. It threads into the bottom of the float bowl assembly, feeding fuel up through the needle jet.
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This number shows up across a wide swath of Amal carburetor listings in the catalog - Monobloc and Concentric type carbs fitted to unit and pre-unit Triumph twins from the 3TA and 5TA on up through the T120, TR6, T140, and TR7RV lines. Given how many different carburetor figures list this same jet number, it's clearly a common size used across multiple models and years, but the exact jet a given carb needs depends on that carb's original tune - don't swap jets around between bikes without checking what size that carburetor called for.
Main jets are one of the easiest carburetor parts to get wrong when guessing at replacement, since the number stamped on the jet is the actual metering size, not just a part number. If you're rebuilding a carb and need to match what was originally fitted, pull the old jet and check the number on it before ordering, or come by the counter and we'll help you sort out what the carburetor wants.
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