| Also known as | 114-038-78E, D358 |
| Diagram | Fig. 11 — CHAINCASE AND CHAINS · ref 8 |
| Subsystem | primary |
| Listed in parts books | 1964–1970, 1974 |
Primary chain, Duplex 78L
This is the primary chain, a duplex (two-row) endless chain with 78 links, living inside the chaincase between the engine and the clutch/gearbox. It's the drive that transmits power from the crankshaft sprocket to the clutch basket, and it takes a beating from oil bath conditions and stretch over time. The catalog lists it under 60-0358, with the older reference forms 114-038-78E and D358 showing up in earlier parts books for the same physical chain.
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Being endless (no masterlink), it's built as a continuous loop, so fitting one means the chaincase and clutch assembly have to come apart enough to feed it through, not just splice a link in. Catalog appearances for this chain run from 1964 into 1974 in our records, which lines up with the unit-construction smaller twins in that era, though we'd want to confirm exact model fitment against what's on your bike before you order.
If your primary drive feels loose, rattly, or the chain adjuster's run out of room to take up slack, this is usually the part behind it. Worth checking the chaincase for wear on the guides and the tensioner blade at the same time, since a stretched chain often takes a toll on those too.
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