Triumph Repair: cd-150 carburator, adjustment screw, upper tube

Question
QUESTION: I have a single Stromberg 150 CD carburetor in my 1977 MG Midget (same as spitfire).  I have rebuilt the carb very carefully and now the car runs very good but very rich (It ran rich before also).  I have double checked float levels and everything else but no luck.  I am not using the air pump.  Is there another needle I can use or wat else could it be?   Thanks, Rusty

ANSWER: Hi Russell,
Put a 3mm Allen wrench down into the top pot after removing the damper and see if you have the adjustable needle. If you find that you do turn the Allen wrench clockwise to richen and counter clockwise to lean the mixture.

Question, how did you determine that the engine was running rich?
Howard

---------- FOLLOW-UP ----------

QUESTION: I have the 3mm allen adjusting tool and have tried all different settings.  I have tried up to three turns in the lean direction and still the car idles erratically with gasoline odors at the tail pipe.  When the gas pedal is pushed to clear it out there is black smoke for a brief time.  Also black soot in tail pipe.

Rusty

Answer
Hi Russell,
Counter clockwise is lean so you need to remove the top pot and look at the needle and the condition of the diaphragm and note if turning the adjustment all the way to the counter clockwise direction pushes the needle down. If the spring lock that holds the adjustment screw is not seated all the way down in the top tube the adjustment will not go down as needed. To check this put the piston down on a solid surface that has a hole in it to accept the needle as you must not damage the needle. Then take a metal tube of any kind that will just fit into the upper tube of the piston and use a light hammer and tap the tube down so as to completely seat the spring clip that holds the adjusting screw down to the bottom. If it moves at all, that was your problem. Look at the set screw in the side of the piston to see that it does not look like someone has put a odd screw in place of the original. If you remove the screw you will see that it has a unthreaded end that is a guide for the jet needle assembly to slide on and if someone has tampered with that screw the the needle assembly may not even move when you adjust it.
If this is not clear enough you need to purchase a manual to see a breakdown of the adjustment system so you can see what I am telling you.
These Stromberg carburetors are not noted for running rich and in fact are noted for running too lean so something is drastically wrong with yours. And you are correct about the black smoke being too rich.
You also need to check the choke system as they are also noted for failure on these carburetors.
let me know,
Howard