MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Adjusting Zenith Stromberg Fuel Mix

I took my 1977 B which was running perfectly to a British repair shop because the Zenith Stromberg 175 CD was leaking a slight bit of oil and to have a quick check up. A new diaphram later, out comes my NGK spark plugs and in goes Champion 415's and the carburator was leaned out because it was running to rich (there were some evidence of carbon on the plugs coming out) the car afterwards ran no where near as good as it did going in. Harder to start,rougher idle and an annoying slight popping backfire on de-acceleration. I want my baby back and to get rid of the backfiring. There are no leaks in the exhaust so I am assuming the mixture is to lean. I have adjusted the mixture about three quarters of a turn clockwise to richen but to no success. My question is how far clockwise to richen can I go. Is it possible or not possible to disengage the needle by going to far or not? Any thoughts on how to get it adjusted correcly and any feelings on Champion 415's. Please help if you can. The timing is dead on at 10 degrees at 1500 rpms but I just can't seem to get it back to running the way it was.
JCH Hibbard

JCH---Not sure on your carb --I changed over to 2 HS4s , on another current thread there is an excellent tech article on ZS carbs. But my comment on the plugs, I have never had any luck with Champion plugs in my MGs so have always stuck with NGKs. I know some ppl swear by Champion , but I dont even use em in my lawnmower -FWIW --Gil
Gil Price

Thanks Gil, I haven't changed them back to NGK just yet as I wanted to hear other responses but I think I may end up doing that.
JCH Hibbard

I think this may help:

http://www.sterlingbritishmotoringsociety.org/files/zenith%20stromberg%20tech%20tips.pdf

I agree with Gil. Junk those Chumpions and go back to NGK, quickly!

Cheers, Paul K

Paul K

Thanks Paul I think I'm going to do just that. I had been looking for a good website on the Zenith stromberg for some instruction and was happy to see your link but it would not open. My luck. Anyway thanks for the advice on the NGK.
JCH Hibbard

It wouldn't open for me either, let's try it again

www.sterlingbritishmotoringsociety.org/files/zenith%20stromberg%20tech%20tips.pdf -

Paul K

Copying and pasting didn't work. Google "Zenith Stromberg" and you should see a link titled "Those Damn Zenith Strombergs" It's a tech article by John Twist on the carb, has nice pictures and descriptions.

Paul K

JCH

Here is the John Twist site
http://universitymotorsltd.com/qa-display.php/128

Kent
DK McNeill

Try this http://www.sterlingbritishmotoringsociety.org/files/choke.pdf

Paul Hunt 2

Thanks everyone for your input. Still have a question however regarding how far clockwise or counter clockwise one can go with the adjusting tool. Is it possible to dislodge the needle by going to far in either direction?
'
JCH Hibbard

From my reading you only adjust the needle up or down in the piston if you can't get the correct mixture within the range of movement of the fine control screw and coarse control nut. So in theory unless something is very wrong somewhere, which would need to be fixed first, I'd only expect a small adjustment of the needle to be made to get the correct setting within the range of screw and nut. Also my Haynes says in dismantling to twist the centre spindle of the tool 2 or 3 *turns* to expose the needle housing assembly, before removing the grubscrew which needs to be done before the needle and housing assembly can be withdrawn. This says to me the needle won't fall out just by twiddling the centre of the tool. But I think the Haynes section on tuning the carb isn't very clear.
Paul Hunt 2

This thread was discussed between 08/12/2007 and 13/12/2007

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now