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MG MGA - float level solved but not 7/16th

Checked the arms were approxamatly 7/16 and the needle valves wre the same length. but the fuel level in front carb was at the top of the jet and the rear was down there somewhere. After setting both to approxamatly 1/8 below the jet top, ignoring where the arms were, the mixtures now respond to small adjustments and idle is a true 600rpm and steady. Never did that before ! Checking the bowl heights the front was higher than the rear, they look the same. Why I don't know and I don't care , the tune is fine. I have always thought that the mechanical method of setting the level may have been ok when the cars were new, after 55 years , maybe on some. also with the floats out, there was plenty of petrol in the front and precious little in the rear. Both the floats are the same hight and float. I set the levels on my Riley and used the same method except that they were not so far out. Sean
S Sherry

Sean, the seals where the float chamber connects to the carb can influence the chamber height a little. If the neoprene seals were more compressed on one carb than the other, or maybe someone has used fibre washers to seal the float chamber to the carb on one and neoprene seals on the other. Another thing that needs to be considered is the float jets, are they the correct type on both chambers and are they in good condition. The taper needle type do wear quite rapidly, Grose jets seem to be a better option.
Lindsay.
Lindsay Sampford

Yes Lindsay, you have solved it. I did have a leak at one of the carbs recently and tightened the gland nut , quite a lot I thought at the time. I had rebuilt the carbs two years ago an could not remember that they had newer type neoprane seals instead of fibre washers. All's well that ends well. Thanks Sean
S Sherry

Two different float chamber fixing arrangements.
One uses a banjo stud, with a fibre washer to the body, and a steel washer, two rubber grommets, another steel washer and a nut to secure the bowl.
The other uses a banjo bolt with a fibre washer to the body, and two fibre separated by a thin brass washer under the bolt head.
In either system the fastener is limited by a solid end point, so if you can tighten it more, it is either plain loose, or has the wrong combination of bits. Most common is the rubber grommets being used with the steel washer(s) missing, which leaks AND puts the chamber in the wrong place. Rubber grommets in place of the fibre/brass washers does the same.

FRM
Fletcher R Millmore

Sean, when setting the fuel level to approx 3/8", did you measure this setting with both jets pulled right down?

Frank
F Camilleri

Hi, Sean please ignore my last post on this thread.I will re-phrase my question.
When setting the fuel level to approx 1/8" below the jet top, did you measure this setting with both the jets pulled right down? If so, do you mean measure from the top of the jet head to 1/8" down the hole? Remember the jets are pulled all the way down as far as they can go.
Thanks.

Frank
F Camilleri

Hi Frank, I measured the level with the jets up as they are with choke off. I got this advise from an experienced Racer, who rightly pointed out that setting the fuel level by a mechanical means of a float lever has a lot of veriables and what is important is the level at the jets being correct and both being the same. Sean
S Sherry


Thank you so much Sean. I seem to have the same problem with my carbs. But I always thought that the floats have to be set at 7/16ths no matter what. The fuel level in my carbs differ at this setting. Thanks to you Sean, I now know that this setting becomes irrellevant after 50 odd years or so. I shall set the floats to get the fuel level to 1/8th of an inch below the jets top, irrespective of what floats setting to use to come to this measurement. I'm now hoping that, after having done this, the idling becomes steady and a pleasure to listen to.

Frank
F Camilleri

This thread was discussed between 17/08/2010 and 23/08/2010

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