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MG MGB Technical - running rich

I had my SU's rebuilt last year because float was sticking. It still runs real rich. I didn't have tuned at the time and the shop that rebuilt is a MG pro.Do they normally run rich? Tailpipe is black soot, plugs (which are new) have lots of soot on them as well. Suggestions? Thanks
Dan

Dan
They don't normally run rich unless the carbs are faulty or out of tune, if you are not sure how to set the mixture yourself take the car to an MG garage and get them to set the carbs. Running a car with an over rich mixture will damage the engine in the long term due to petrol washing the bores.
Ron
R. Algie

Check the float level too as that can cause a rich condition. I would also look at the needles and nozzles to check their condition. If you can't eliminate the rich condition by making the mixture leaner a new set of leaner needles may be in order.
Mike MaGee

Is there a solution to adjusting the floats when all that's available is a cheap non-adjustable plastic float?
Jeff Schlemmer

The non-adjustable float is adjusted by different thicknesses or combinations of gaskets under the needle seat. A rebuild kit will come with several to choose from. Ask anyone who works on them as they will likely have several extras lying about.

As far as rich is concerned... Are the air filters old? A clogged filter will make the ol' girl run rich. Remove the air boxes and check the filters, replace if necessary. Then look for a small pin just behind the flange to which the air boxes bolt. It hangs down vertically below the piston (under the "bell"). At idle, lift up on the pin all the way. If the engine note rises a little then falls off the mixture is good. And now I'm having a brain fart as to what it means when the note rises and stays there (I seem to recall that is rich) but the exhaust note is "splashy." Of course, if the note falls off immediately it is the opposite (as I seem to recall that would be lean).
If it is rich, turn the adjusting nut on the needle CW 1 flat (UP, do both carbs the same) and check again. I like to push up on the end of the jet from underneath after turning the nut and blip the throttle before checking with the pin again.

Once it is correct at idle, clean the plugs and drive for a few days. If the plugs indicate rich still, you may need a lean needle. If the plugs are not dirty with dry fluffy soot, but nasty shiney gunk then it is the PCV system, not the carb.

Mike!
mike!

This thread was discussed between 10/06/2004 and 15/06/2004

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