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MG Midget and Sprite Technical - Wobbly Float Chamber!!

Hi All

I got the old girl(MKII '66) through the MOT last week with no advisories....

It seems that the float chamber on the front carb is loose in that it has free movement of about 1/8th of a turn. The rear one has minimal movement. Is this something that will be cured if I rebuild them with one of the SU kits or is there something else I should be looking for?

Tony
Tony Brough

Tony if I understand you correctly the float chambers do move, as far as I know, the rear one may move less as it may have (more) crud holding it back

if you spray the rear one with carb cleaner you may find that it moves an 1/8th too

if you clean the whole of the carbs remember to relubricate them too
N Atkins

Thanks Nigel

I cleaned all the crud out last year and relubed them to, it just doesn't seem right, but maybe I am just looking for something to do next......
Tony Brough

servicing and maintenance is a regular ongoing process Tony :)

if you've done all the servicing, maintenace and repairs on your car then you should be only concerned with how much you can drive it (whilst the weather holds) :)
N Atkins

There should be a slight amount of movement to stop frothing inside the float chamber but 1/8 of a turn is excessive.

This means that the nylon adapter between the float chamber and carb body is worn, the rubber washer is worn or the bolt is simply not done up correctly.

See:

http://www.rimmerbros.co.uk/Item--i-GRID005606

(ok it's a Spitfire 1500 reference, but the parts are the same)


Specifically we are looking at parts:

AUD2891
AUC1318
AUD2178/AUD2179
Deborah Evans

good point by Deborah

I must admit to not taking an 1/8th of a turn to literally to mean 45 degrees more just an expression, my mistake good job it was spotted

sorry Tony
N Atkins

The adaptors - AUD2178/AUD2179 - are vehicle specific and are used to set the angle of the float chamber with regard to the carburettor body.

For example, the Mini Cooper and S used a different adaptor to the midget/Sprite due to the much steeper angle of the inlet manifold tilting the carbs upwards. The adaptor keeps the float chamber vertical.

On older SUs, the adaptors were metal rather than plastic/nylon, so it is possible that it is completely missing.
Dave O'Neill 2

Indeed Dave,

However the Midget 1500 set up is EXACTLY the same as the Spitfire 1500 set up.
Deborah Evans

I can't seem to see Tony's reference to a Midget 1500 anywhere.

Your point is?
Dave O'Neill 2

That your post could be interpreted by those 'not in the know' that the Spitfire diagram and part nos I posted would not be suitable for a Midget 1500, when in fact they are.
Deborah Evans

just as I did Deborah made a (different) mistake by putting the parts are the same but the illusration was to highlight the parts required

Tony put >>(MKII '66)<<

I could have put up a page with the parts for a Mk2 '66 but Tony is an adult and would know to check for exact part numbers and I'd guess be able to find the information from Deborah's lead

forum postings are very useful but because of what they are not always 100% accurate to the given specific details

as you know I find it difficult to read and type within the forum and I know I'm not alone in misreading or misinterpruting things from this method of communication

N Atkins

Doh!

I've been answering too many 1500 Qs recently and missed the fact that Tony has an A series car!


Mea Culpa!
Deborah Evans

Thanks for all the posts.

Deborah, although the part number may be different it pointed me in the right direction and the Moss site illustrates the part for my carb (AUC1367/6)although SUCARB.co.uk list them at almost half the price, I just need time to get the carbs off and see what is wrong, rather than my previous fault finding methods of replacing all the bits until it works correctly, then realising that the the first 10 or so parts where OK after all.


I will post back with the outcome.

Cheers

Tony
Tony Brough

Tony do a Prop and look at it from the opposite direction - pack some crud round it so it can't move as much!



or more seriuosly, check the bolt tightness first and the term loose, it turning by hand is a different matter to swinging freely
N Atkins

90% of the time the bolt is just loose. Helps to remove the screw holding the choke link to the jet, but a thin & slim spanner will usually do. It's a shouldered bolt and is to be tight against the shoulder. And if you do have to replace the bush and grommet, you can do it in-situ as well. You do have to disconnect the link to replace the grommet under the bolt head, but not the bush. Do not lose the brass distance bush where the screw goes through the link - they are usually captive, but sometimes fall out.

FRM
FR Millmore

This thread was discussed on 04/07/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.