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MG Midget and Sprite Technical - SU H1 lesking

The rubber between the float chamber and the carburetor lasts only one year. (the carburetor is positioned above the outlet manifold...) Is there a solution?

Flip

Flip Brühl

Hey Flip.
I don't have an H1 to look at so this may be nonsense, but is it possible to use a copper washer?
Greybeard

Greybeard, I have seen something like you suggested on the Burlen site. but the rubber is a few mm thick. now I have the rubber Grommet (7).

Flip

Flip Brühl

From the diagram it looks like there are 3 alternatives.
Parts 3, 9 and 7 are one, parts 5, 4, 9, 7 and 8 are another. The third is parts 2, 5 and 6. The last alternative doesn't use a rubber gromet. You could try that alternative.

Rob
MG Moneypit

Well how curious. My SU book says rubber seals too, but it's not very helpful beyond that.
That looks like a banjo joint in your photo and I am used to finding copper rings in them. I mostly work on big diesels and they are almost universal on the fuel banjos. They seem to work well in my experience.

Rob's post is interesting.
Greybeard

Flip,
It could be that the rubber doesn't like ethanol in petrol (recall that we've had to change petrol hoses to an ethanol spec) - see if you local seals supplier can get you the same size in Viton - which looks and acts like nitrile rubber but is a lot more solvent resistant - theres some googled stuff here http://www.easternseals.co.uk/viton-fkm-vs-nitrile/
timmyk

The workshop manual says rubber washers on both faces, with a steel washer between bolt head and bottom rubber, and the top rubber direct to the carburettor body. Can't see the steel washer in your picture, Flip, but I guess it's there. All the H carburettors I've had were on rubber washers, and you can swivel the float chambers a little, but without getting a leak that I can remember.
Nick and Cherry Scoop

Apologies for not checking in my carburettors box before writing.
My H1s are fixed up like Rob's 5, 4, 9, 7, 8 set. It puts the float chambers 3/16" lower than in the original set-up.

Flip - your rubbers look a bit stressed. Maybe this (presumably later) design with its big steel washers maintains the shape of the rubbers better.

BTW, these carbs were overhauled professionally in 1980.

Nick and Cherry Scoop

Yes indeed the rubber is stressed. I use E 95 fuel. I bought the rubber from Burlen. I have a concave washer under the lower rubber. Hollow side up. should it be hollow side down?

Flip
Flip Brühl

Flip,

Do the seals actually leak or just looked cracked. From my engineering degree years ago it was mentioned that perishing of rubber parts decreases with the square of the distance from the outside surface but in this case it may depend on what is causing the degradation.
David Billington

Flip,

Is the 5, 4, 9, 7, 8 set still available from Burlen? I've been contemplating it (next to me on the window sill for the last three days), and it seems to me the best of the three options:- a static central bolt, separately sealed to the carb body, with a sandwich of thick flat washers holding the rubber seals in place, tightened NOT by a revolving bolt which may turn and stress the rubbers, but by a nut, which will not disturb them.

Nick and Cherry Scoop

I tried the 2 5 6 alternative, Rob's suggestion, it works!

AUC 1541 holding up bolt
AUC 2130 fiber washer
AUC 5027 fiber washer
AUC steel washer

I also removed and polished the groves in the float chamber connection.

Flip

Flip Brühl

That's good information. Good post Flip.
Greybeard

Sorry aug 5026 steel washer.

Here a photo go the polished end:

Flip Brühl

This thread was discussed between 14/04/2018 and 18/10/2018

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