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SU carbs running too rich

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Andy you may be right but as the shoulder is proud of the Brass bit I'm assuming it's flush with the aluminium face of the dashpot itself.


If not put a straight edge across the face and pull the needle down to it, the job's done.


Apart from a tendency to flood (for me and my son only?) SUs are dead easy IMO.



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Hello to all.


As I wrote earlier, I lowered the needles by about 0.5 mm below the piston face and tested again the engine. With the jet nut at its uppermost position, there was a clear lean mixture operation symptom.


I was able to achieve around 5% CO in the exhaust by turning only 3 flats (half turn) in the jet nut, what seems to be too little (recommendations are around 6 or 9 flats), and surely the problem of too large a jet orifice still persists.


The engine seems to run fine, but I have still to test the spark plug conditions after a serious drive.


In all, I hope that changing to new jets, the situation will improve, and I will try to go back to the correct needle position.


I'll post the news.


Thanks again for your help.



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