Leaking carburators


Both carbs of my XK140 FHC are leaking fuel. It’s dripping (see attached pictures)

The needle and seat (controlling the petrol flow are ok). Both floats as well.
What could be the root cause for my leaking carburators?



There are cork and fiber seals in there.
You need to replace them all.
Moss, Burlens, SNG et al should have those seals.
The one down inside the lower hex cap that you have already removed is a special size, ID and OD carefully manufactured, so don’t try to substitute something else in there or it will drag on the mixture adjustment screw.


When replacing those cork seals I was advised to soak them in oil overnight prior to fitting them, this from the company who at that time held the S.U. distributorship in my neck of the woods.



I never fully stopped those leaking… despite the carbs being completely rebuilt.

Check the needle seat diaphragms. Mine were brittle and cracking. These things only move when the mixture is adjusted.

Harry has the H6 carbs, no diaphragms to worry about.
It took me a couple of tries to get the cork seals right.
This job is best done on the work bench, not on the car.

I often have a black drop of oil on one of them, at the same spot

Some people including myself have replaced the cork seals with Teflon O-rings. H4s have 1/4" jets, so they need O-rings with a 1/4" (nominal) I.D. The actual I.D. is very slightly smaller. Not sure about H6s. Teflon O-rings will NEVER leak.

Bob Frisby
Boise Idaho

Thanks all for your reply.