| Diagram | Fig. 2 — CARBURETOR AND AIR CLEANER · ref 13 |
| Subsystem | fuel |
| Listed in parts books | 1968, 1970–1974 |
| Also fits (as replacement) | 1968–1970 · for 99-0522 |
O-RING (THIN) CARB FLANGE
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This is the thin carb flange O-ring for Amal Concentric carburetors, part number 622/101. It seats between the carb body and the intake manifold flange, sealing that joint so you don't pull unmetered air past the carburetor mounting. It shows up across a wide run of Amal Concentric carb figures in the parts books, including the T100 family carburetor listings, from 1968 into the mid-1970s.
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This one is the thin version, so don't mix it up with the thicker O-ring used on some Concentric setups - if your old ring looks noticeably heavier, you probably want the other one. This part number replaces the earlier factory number 99-0522, so if your bike's old parts book lists that number, this is the current equivalent.
It's a cheap thing to overlook, but a hardened or flattened flange O-ring is a common source of a lean, hunting idle that owners chase for weeks blaming the jetting. Worth pulling the carb off and having a look if you're chasing an air leak at the manifold.
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