| Also known as | 40-243 |
| Diagram | Fig. 3 — CRANKCASE · ref 46 |
| Subsystem | engine bottom |
| Listed in parts books | 1969–1970 |
BSA Oil seal, primary case back
Oil seal for the primary case back, listed in the crankcase section of the parts books.
This is an oil seal for the primary case back, listed under part number 40-0243 (also shown as 40-243 in some records). It shows up in the crankcase section of the parts books, where it does the job of keeping oil where it belongs as it passes between the crankcase and the primary side of the engine.
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Our catalog record ties this one to appearances spanning 1969 to 1970, though we'd want to confirm exact fitment against your engine before you order rather than go on the number alone.
If you're rebuilding the bottom end or chasing an oil leak at the back of the primary case, this is the kind of seal that gets replaced as a matter of course while things are apart. Call the shop if you want us to check it against your specific engine casing before it ships.
We've never carried this one. Tell us what you're after and we'll go looking — you'll get a price and photos before you commit to anything.
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