400 four main jet o ring

[exvalvesetdabbler]

Found these,  6.5OD x 1.2CS. in viton.

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They are a nice fit.

Regards and seasonal greetings
Dave

[SeanFD]

These are a perfect proven fit.1.2mmx3.5mm buna n70
Qty 36 was under $8.00 us

Are the dimensions reversed? 3,5 ID and 1,2 CS?

If so they are available here, though still not too cheap.

https://www.polymax.co.uk/catalog/product/view/_ignore_category/1/id/161306/s/o-ring-3-5mm-id-x-1-2mm-cs-fkm-viton-75-sha/category/9999/

[exvalvesetdabbler]

You have to carefull with Chinese suppliers, some, not all give OD and CS which is not the
convention in the UK

So taking 6.5 od -2 x 1.2cs gives 4.1 X 1.2 (ID x CS)

Regards
Dave