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MG Midget and Sprite Technical - SU carbs - spindle bushes and needles

Got my service kit. Took them apart. I then discovered about 1mm of play in the throttle spindles :o( They looked ok when fully assembled. So I have a technician at work all set with the milling machine. Can anyone help on the bush size? These are AUD327 carbs and I believe I need 4 AUD3079 bushes and two WZX1310 spindles. What size hole do we need to put the bush into?

Also, whilst they're in bits, anyone know which needles I should have for a standard setup? Just want to check I have the correct ones. This is a 1971 1275cc.

All assistance appreciated, as ever. 11 days till it's the wedding using wedding cars tonbridge car!! :o)
Ant Allen

Ant,

When i did mine i ('72, 100K on clock) found that with new spindles they were fine - most of the wear was in the brass shaft not the carb body.

But i had more time ! Best of luck.

Richard.
richard boobier

In the USA for a 71 its "AAC", in the UK, I have a gut feel that its "AN" with the light blue spring for both, Give moss motors a call to there tech support, they will know and are all ways glad to help.

Id send the maintance kit back and get a "repair kit" this kit has the bushings, shafts, butterflys and the special little screws for the butterflys, you will also need a reamer for reaming the bushings after they are installed....As to the drill hole size, Sorry I cant help you there but I think most quality kits give that info...if not give Moss a call or better yet give burlen a call, they are the company that makes SU

here is a tip...take only one carb apart and rebuild at a time, that way you all ways have another carb to look at for figuring out how the linkage springs and linkage goes back in...looks simple but vary tricky from memory.

also when you get them disassembled and cleaned, boil them in water for 5 minutes, let cool, then use fine/medium steel wool, and give them a good polishing, they will glow like chrome... The boiling makes them "scale up" more and brings the impurities of the aluminum to the surface of the metal so that its easier to polish out with the steel wool.

luck
Prop
Prop***The End in 2012

Ant,
Like Richard, I have found that a new standard shaft sorted the play without worrying about the carb body. It was nice of them to set it up so that the shaft was soft brass. Worst case, I believe you can buy over-size shafts and your friend can machine the carb body to accept them.

If your throttle plates have the valves in them, I would recommend you take advantage of the opportunity and replace them with the plain ones. Perhaps the Brit ones didn't come that way?

ISTR stock needles for your carbs should have been the ABC.
David "simple as,,," Lieb
David Lieb

>>>>>ISTR stock needles for your carbs should have been the ABC.<<<<<


Please dont tell me Im wrong agian, I hate being wrong!!!, I thought the ABC needle came out in 73 with the smog junk, at least thats what I wrote down in my BOOK of midget notes.


Prop
Prop***The End in 2012

Thanks for the help guys.

Having examined the shaft on the most worn unit it does indeed look like only the spindle is worn. New spindles and bushes arrive tomorrow but hopefully I'll only need the spindles. Thanks for the tip on that one - it may just save an evening in the machine shop!

Needles - Someone at work produced an SU carb book this afternoon (now that's service!). Prop's correct, I should have AN needles. The ones in these carbs say "H6" on them. What's a H6?

Ant
Ant Allen

Ant,

H6 is the richer version from standard AN, often used with better aircleaners/tub manifold etc ISTR.


Richard.
richard boobier

OK. I still have the old carbs so I'll have a look what needles are in those tonight.

How much difference will H6 rich needles make over AN standard needles? Apart from rebore to +40 my engine and intake system is all standard.

Ant
Ant Allen

This thread was discussed between 07/04/2009 and 08/04/2009

MG Midget and Sprite Technical index

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