| Also known as | T1727 |
| Diagram | Fig. 11 — CHAINCASE AND CHAINS · ref 25 |
| Subsystem | primary |
| Listed in parts books | 1964–1965, 1967 |
PRIMARY COVER 63-67 650
Primary chaincase outer cover for 650 unit-twin Triumphs, cataloged for the 63-67 range.
57-1727 is the primary chaincase outer cover used on the 650 unit-construction Triumphs, the piece that bolts over the primary chain and clutch to keep the oil in and the road grime out. The catalog ties this cover to the 63-67 650 twins, and it shows up in the CHAINCASE AND CHAINS section of the parts book, which is exactly where you'd expect an outer primary cover to live. The older book number for this same part is T1727, and it also carries the 9998-897 form, so if your parts book or an old invoice lists either of those, you're looking at the same casting.
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On these machines the primary cover is a stressed sealing surface as much as a cosmetic piece - it mates up against the inner cover and gasket to form the oil bath the primary chain runs in, so fit and gasket surface condition matter more than they might on a purely decorative part. Given the narrow year span in our records, double check what's currently on your bike before ordering, especially if a previous owner has swapped covers or crossed parts between years.
We don't have more detail on this one beyond what's in the parts book listing, so if you're not sure it matches what's currently on your chaincase, give us a call and we'll sort out the fitment before you commit to it.
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