| Also known as | O648 |
| Diagram | Fig. 20 — TELESCOPIC FRONT FORK · ref 40 |
| Subsystem | forks front |
| Listed in parts books | 1974, 1976–1980, 1983 |
Cap Screw, Top Cap Nut
Inner fork top cap nut that captures the fork spring inside the telescopic front fork, used with disc brake front ends.
This is the fork top cap nut, the inner nut that sits inside the top of the telescopic front fork leg and captures the fork spring underneath the outer cap. It's a two-piece arrangement — this inner nut has a locating tip that holds the spring in place, and it gets covered by an outer cap that threads over top of it. The catalog shows this part turning up on the front fork and, oddly, cross-referenced under an exhaust pipes and mufflers figure as well, so don't be surprised if your parts book lists it more than once.
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The legacy number for this one is O648, which is the form you'll see in older parts books before the 97-4387 numbering took over. Catalog appearances for this part run from the early to late 1970s, on forks built for the disc brake front end.
If you're rebuilding a fork top assembly, get both the inner nut and its matching outer cap sorted at the same time — the two work together to keep the spring seated correctly.
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