car was running rich (black sooty smoke) so I fiddled with the mixture screw under the carb and fixed that problem, now it idles in an irregular way, reving high then almost cutting out. I have tried to adjust the idle screw but really it still is up and down. Have i now made the mixture too lean and starving it of fuel ?

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1977 Clubman

i am not an expert on the problem you have but make sure there are no air leaks in the system and that your carby is nice and clean. what engine do you have and if it has mods, what has it got? make sure you have the right needle for the job. make sure your timing is set right and that your dashpot has oil in it, filled to the correct level. clean out your fuel bowl and check the needle and seat in the top of your fuel bowl. there are many things that could cause irregular idleing but it most likley the simplest thing that is the problem.

if it didnt do it before then i would definatly say its running too lean and needs richening up, but who said you have the right needle in to start with.
check the needle and then check for air leaks and set the jet in the correct posistion and work from the beginning.

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www.minicranks.com add me to your watch list and come back again soon, under construction.

Jai, I wouldnt have thought a needle would change the Idle Mixture ... ?

I thought they were all pretty much the same in that area......

Sounds like a vacuum leak to me.... with the engine idling fast (raise the idle speed about 1000RPM) Spray some WD-40 or similar around all the areas air could get into the inlet.... from the carb/manifold join and all the way through to the head.. include vacuum lines and carb throttles (from the side)

A change in idle will let you know there is a leak in that area.... now you know where to look for a problem !

Enjoy
J

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Will do

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1977 Clubman