O-Ring Placement

[750turboguy]

These two o-rings....

Put them on first and then the gasket OVER them or put the gasket on first and then the o-RINGS?

[JezZedexE1]

There are a couple of threads you can take a look at. It might help clarify matters.

viewtopic.php?t=11247
viewtopic.php?t=15663

I have them on an engine I have, US bike. Those two studs are open at the bottom. On the other side without the o-rings, they are blind holes and do not go through. See images. The one from the old post shows the holes from underneath, inside the casing.
.

Screenshot 2026-01-01 083132.jpg (164.03 KiB) Viewed 1955 times

Screenshot 2026-01-01 082537.jpg (121.36 KiB) Viewed 1955 times

Screenshot 2026-01-01 082455.jpg (195.59 KiB) Viewed 1955 times

Screenshot 2026-01-01 082558.png (573.04 KiB) Viewed 1955 times

.
My take is if you use them, they go on first and then the gasket. Would need confirmation on that though, as I am not really up to speed on these things engine-wise.

[Würstchens-Turbo 810]

It's been quite a while since I had the engine open.

But I think these O-rings go under the base gasket; they sit in the groove around the stud, right?

Alternatively, you could remove the studs and reinstall them using thread sealant.

[youngblood]

I have always fitted these O-ring underneath the gasket.