I'm surprised you don't have a manual for reference. They usually have a pretty
good description and some illustrations to help with questions like these.
Don't be intimidated, SU carburetors are about as simple as they come.
1. If you have a bowl overflowing and remove the cover the float should pop to
the surface. If it doesn't rise is is full of fuel.
2. The fuel control needle valves are evidently working. If they have conical
tips they are not Grose Jets as those use a ball in a seat to seal.
3. OK
4. See 2. above. These are actually not the jets, but are needle valves that
control the fuel level in the bowl. The best have a conical viton tip which
provides a resilient seal. Some have a small spring loaded rod at the float end.
5. The needle valves fit into a brass valve body that is screwed into the bowl
lid. The needle and valve body are usually replaced as a set. There should be a
gasket between the valve body and the lid.
6. Yes, the diaphragm seals the fuel circuit and if it is cracked or split fuel
will leak as you describe. The fuel in the manifold might indicate that the
float/needle valve is set too high. If the float is too high the fuel level in
the bowl will allow fuel to siphon into the manifold. The jet is the machined
tube attached at the bottom to the diaphragm and sticking up into the venturi
bridge. When properly set up you should be able to activate the fuel pump and
remove the dash pot assemblies and see fuel within a one or two millimeters of
the top of the jet at the bridge. That indicates the proper float level.
Enrichment is done by pulling the jet down into the bridge. With the jet needle
in place that action enlarges the orifice the fuel is pulled through and thus
increases the amount of fuel permitted to enter the venturi.
Good luck.
Bill Lawrence
BN1 #554
________________________________
From: Healeys <healeys-bounces at autox.team.net> on behalf of ph <yosmovies at
hotmail.fr>
Sent: Tuesday, May 16, 2017 10:06:10 PM
To: healeys at autox.team.net
Subject: [Healeys] Carb tsunami
We are working on my early phase 2 BJ8. Very standard car.very standard fuel
pump and system.
So, we've noticed that petrol was initially seeping out of the front carb, HD8.
Then the seepage seemed to get worse, almost as we looked at it. The leak is on
the front carb and the fuel seems- it's not easy to be sure- it seems to be
coming out from where the choke cable hits the lever. Given sufficient time and
particularly a few attempts to start the car, then the fuel comes out of the
manifold overflow pipe. Plenty of it too.
Some observations:-
1) both of the floats are good. 100%
2) no fuel at all ever comes out of the float chamber overflow pipes
3) the connections at the banjos are sound.no leaks there
4) the jets??I don't know, are they Grose? They are kind of octagonal in their
long profile. They have a little spring inside, with traditional cone shape at
the top and little short, spring loaded, needle sticking out of the bottom. One
of these things appears to be white nylon/plastic plus brass and the other
appears to be some low grade silver coloured alloy. Both springs appear to be
functional and both jets can entirely stop fuel coming out. (ie when I close
them/push them home by hand). But we know nothing of these things. Never seen
one before.
5) Not withstanding my suspicions of these seemingly complex little jets, we
think they are correctly setup. They are not dropping so far that they can jam.
No, we think that the jets are probably, note probably!!, OK.
6) My uncle, who is over from England, is more used to HS4s and Webers but he
is wondering if the problem could be from the diaphragm. If it splits, that's
it, right? Fuel in the manifold, fuel on the floor??
We'd really appreciate your accumulated wisdom. If we're to get the parts over
from the UK, we've got to order them yesterday!!
Pierre-Henri
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