Sending Unit Gasket, why your old one leaks:

[elwood440]

Somewhere on here I had read that a re-used sending unit gasket will "reliably leak," or something to that effect. I am working on mine presently, and took some new-vs-old pics of the gaskets. This is one of those parts that must be changed when you disturb the sending unit, and it is always recommended to replace it with a genuine Honda part.

Below I think you should be able to see for yourself WHY an old gasket will not seal.

[Earl43P]

I rejuvenated mine with brake fluid and it has not leaked.
I was careful to "seat" it back exactly as it came out.

[mrtwowheel]

40 years old and I've reused it over and over.

Scott

[elwood440]

Given the choice between trusting the one on the left, or paying $3.26 plus shipping for the one on the right, I'm going to go with the one on the right. That's just me though. YMMV

[roachb]

I certainly replaced my original gasket about 8 years ago. But I recently had it out and it looked fine so I put it back in. No problems. But I would not reuse the one on the left, for sure.