Rubber gasket for Lucas L679 lens

Hi all,

This is actually a query concerning most brit bikes made between 1964 and 1973, but I will post it here, since by number most Commando models had the L679 lens.

The rubber gasket carries part no. 54571677. The NOS sample shown features a lip surrounding edge of the lens.
However, all aftermarket rubber gaskets do not have this lip. There is a US company reproducing the rubber gasket and they claim their original (?) sample doesn't feature a lip.
This kind of gasket appears to seal poorly, as there is no even clamping pressure. I have no idea how well the lipped gasket actually seals.
Hence my question, was the original Lucas rubber gasket supplied in different versions, and if so, was the lipped or non-lipped gasket the last one?

- Knut

mdt-son said:

The rubber gasket carries part no. 54571677.

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That is the only part number for the gasket I can find, however,...

mdt-son said:

NOS

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...although the gasket appears to have been in the correct part number box it seems to be a used or previously assembled part because it has the imprint from the metal base plate (unless you removed it before taking the picture, however, the base plate has a different part number)...
54578212


...and what looks like a groove is perhaps an imprint from a lip inside the lens.

L.A.B. said:

That is the only part number for the gasket I can find, however,...

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You are probably right. Lens has a recess along the inner circumference which creates the bespoke imprint (no lip). I tested the effect with a strip of paper.
Thanks for looking into this, LAB!

- Knut

Doubt there is much sealing other than splash protection going on with either of these or even the later 850 style rectangular lamp box seal.