[Mgs] MGB Carb Qs

[Hans Duinhoven]

Bent needles may indicate damaged jets.

Needle type is dependent of air filter type a.o.

Look for cross reference tables for best needle type to choose.

Also the HS4 carbs were produced with various changes over the years.

Hopefully your carbs still bear sub model indicators attached to the float
chambers, so you can dig deeper into the best combination tables.

 

An example like this in on my 1971 BGT, which is equipped with the latest
variant of the HS4 carb.

This carb is equipped with the "swing needle", which were common on the HIF4
carbs. 

 

HS6 carbs were not the standard carb for the MGB (too big).

 

Stock air filters are carrying paper filters, which should be exchanged
every 8000 miles or so.

Pancake shaped airfilters like the K&N make maybe equipped with metal
filters, which can be washed clean.

These filters have less air restriction, so a different needle should be
chosen to give a proper mixture and engine operation.

 

Hope this helps a bit.

 

Good 2018!

 

Cheers,

Hans

 

 

 

 

See below:
On 12/26/2017 5:45 AM, daybell7--- via Mgs wrote:



I plan to replace the weber (45DCOE) with HS4s on my 1968 GT.  The needles
are bent and a float is missing.  Is it reasonable to expect success by
replacing these parts (and maybe jets and float valves), after a good
cleaning?  What needles and jets?

 

    It would be a good idea to send the carbs off to a rebuilder. They would
know what's needed.



I have shiny carb air cleaners to use on my 1972 Roadster with HIFs, but
when I replace the stock air cleaners, the car bogs and won't accept the
throttle.  Should I change jets?  What jets?

    Sounds like the filters are clogged.  Clean or replace the filter
elements and try again.



 

Should a car start without choking?  Is that a indication of a rich mixture
if it does?  I have a car with HS6s that fouls the plugs when I start it and
move it in and out of the garage, but don't drive it.  The car needs choked
to start but once started the choke can be relieved immediately.  Do I have
a mixture issue?  Do I need a meter?

     Are the jets free to move up & down?  Sounds like they are but don't
move far enough up when the choke is pushed in.  
    Could be a matter of jet adjustment.   If it's fouling the plugs with
dry black residue it's running rich.  If the residue on       the plugs is
wet & oily the rings are leaking.   



 

The weber runs rich and, I suppose, can be corrected changing jets.  Can
anyone point me in the right direction in all this?  Maybe a supplier that
has explanations?

     You seem to have a fixation on the jets.  The Weber running rich could
be a matter of the float height or a leaking float.
     Is there a MG club in you area?  You need a knowledgeable person to
look at all of your carbs.



CR

 



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