| Diagram | Fig. 15 — CHAINCASE AND CHAINS · ref 24 |
| Subsystem | primary |
| Listed in parts books | 1976–1980, 1983, 1985 |
'O' ring
An 'O' ring for the primary chaincase, likely sealing the inspection cap on later-style covers.
This is the 'O' ring used in the chaincase area, on record under part number 71-3896. It shows up in the parts-book figure covering the chaincase and chains, and one of our other listings ties it to the inspection cap on the later-style primary cover.
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The job of an O ring like this is straightforward: it seals a joint so oil stays where it belongs instead of weeping out around a cap or cover. On a primary chaincase that means keeping the chain oil bath sealed up so you're not losing lubricant or making a mess on the garage floor.
Our catalog record spans appearances from 1976 through 1985, but that's just the range across all the listings this part number shows up in, not a guarantee it fits every bike in between. Check what inspection cap or cover you're working with before you order, and call the shop if you want us to confirm fitment.
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