BST38 Float bowl drain screw o-ring?

[Crass]

There is a small o-ring with the Wemoto carb gasket kit for the BST38s that I can't match up to anything existing on the carbs. The only thing I can think it fits (which it does) is the float bowl drain screw but mine don't have any, nor does the parts fiche show one. Should an o-ring be present?

[Nick]

Never seen o rings on drain screws on thr float bowls.  You sure it isnt the vacuum port o ring for the top cap?  Or the mixture screw o ring?

[TonyGee]

if its tiny it'll be the mixture screws

[Crass]

Nope, it's neither of those. You get the pilot mixture screw o-ring in the pack, this isn't it. It's too thin to work as the o-ring on the carb cap sealing the carb balancing vacuum takeoff. The latter don't come with the set, I had to buy those separately.

See photo - the mystery o-ring at the top. Bottom left is a mixture screw o-ring (smaller) and bottom right is the o-ring for the cap.

Edited November 23 by Crass

[TonyGee]

does the float valve seat pull out like a 1200 bandit 36's ? theirs an O ring round that

[Jaydee]

2 hours ago, Crass said:

There is a small o-ring with the Wemoto carb gasket kit for the BST38s that I can't match up to anything existing on the carbs. The only thing I can think it fits (which it does) is the float bowl drain screw but mine don't have any, nor does the parts fiche show one. Should an o-ring be present?

Hardly this o-ring location? (What TonyGee said)

Edited November 23 by Jaydee

[Crass]

No, it's not that one it's too small and there's another o-ring supplied which fits the float bowl mounting stem.

I'm wondering whether perhaps this kit fits more than one bike / carb and as supplied for a GSXR750L there is an o-ring that is not used?

[Dezza]

7 hours ago, Crass said:

No, it's not that one it's too small and there's another o-ring supplied which fits the float bowl mounting stem.

I'm wondering whether perhaps this kit fits more than one bike / carb and as supplied for a GSXR750L there is an o-ring that is not used?

I think you are right here. Many of the o'rings are shared between different sized BST carbs but there are also probably one or two differences so including an extra o'ring would mean the same kit is suitable for a much wider range of bikes.

[Upshotknothole]

There were at least 2 different versions of the BST38s on the GSXR750s, could be for something not on your carbs.