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MG MGA - float levels

Is five sixteenth the correct float level or is it
7 s/th Different books I have quote different settings. A while ago I had the carbs checked, set and balanced using a modern analiser, it idles at 800 and preforms well. Checking the levels just for fun I found that one carb was a lot lower than the other even though the settings were the same at 7/ 5th. ? ? 5 or 7 ?.
Should I be able to see the petrol hight in the jets , suction chambers off ? Are the float levels cditical on S.Us. Thanks Sean
S Sherry

Hi Sean
I thought it was 7/16.Not sure without a manual handy. Place a 7/16 drill bit under the float fork to set it. Sometimes, in the right light you can see the fuel if you drop the jets. Yes, the level in the float chamber is important. If not set properly the car will run rich or lean.
M S Randell


Steve Gyles


As the other guys have indicated, the fuel level in the float chamber is important because it governs the height of the fuel in the jet. The higher it is, the more droplets will be drawn up by the venturi action of the air passing over the jet. The more fuel is drawn, the richer the mixture, and if the height is not set properly you will find it difficult to adjust the mixture by the usual method.

Look carefully at the diagram in the workshop manual because there is only one good place to bend the fork or you will get a false adjustment. Make sure the fork arm is straight. With the float chamber lid inverted, let the needle valve close completely on its seat and then slip your 7/16th drill bit shaft under the fork. If it does not slip in exactly (neither tight nor slack) bend the fork until it does. Don't try to bend the fork with the drill bit in place. It's worth the hassle of taking the fork off and holding it properly while you bend.

All this depends, of course, on your needle valve actually shutting properly. If it has worn seats, it won't shut the fuel off so you'll get flooding regardless of the fork setting. Fit Grose jets for peace of mind.

And forgive me if I'm stating the obvious, but if your float is letting in fuel it will not float properly and will also cause high fuel levels and, at worst,flooding.

Once it's done, you should be able to reassemble everything and forget it (for a good number of years anyway).


Malcolm Eades

Check your floats for leakage. Over the years they develope hairline cracks allowing fuel to seep in weighing down the float which will need more fuel to float it. Could be the cause of the uneven fuel levels. My original floats had this problem. They did not sink completly but had enough fuel in them to change the level. I had the same trouble with a replacement set except they sunk completly within a few months and fuel poured out the overflow pipes. I am glad the engine did not fire. The floats were nice looking reproductions but the soder job was poor and thats where the leakage occured. I resodered them (tricky job) and they've been fine ever since.
Charles O'Brien

This thread was discussed between 15/08/2010 and 16/08/2010

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