| Also known as | T4018 |
| Diagram | Fig. 13 — INNER AND OUTER CHAINCASE · ref 1 |
| Subsystem | primary |
| Listed in parts books | 1973–1974 |
Cover – inner primary, with fixed fittings
Inner primary chaincase cover with fixed fittings, the plate behind the outer primary case that houses the oil pump mounting.
57-4018 is the inner primary chaincase cover, the plate that sits behind the outer primary case and carries the fixed fittings for the oil pump and related hardware. It's listed under the older T4018 designation as well, so if your parts book still uses letter prefixes, that's the same physical piece.
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This cover shows up in the catalog figures covering the inner and outer chaincase assembly, and specifically the inner primary cover as it relates to the oil pump. It's the part that keeps the primary chain compartment sealed on the engine side and gives the oil pump its mounting point within that housing.
Our catalog record ties this part to appearances across a couple of model years in the early-to-mid '70s. Beyond that, we don't have more detail on it here, so check it against what's on your bike before ordering.
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