XK120 Starting carburetor issue

I am currently rebuilding the 2 SU H6 carburetors of my 1953 XK120 FHC. On the starting carburetor, I appear to be missing the spring and the shoulder washer shown at the very bottom of the picture enclosed. XK120 and XK140 SPCs do not show a part number for those 2 items. From the information I have gathered so far, it is possible (but at this point, I’m not sure) that only the XK140 had the shoulder washer, so maybe I could get away without having this bit. The conical spring, however, is a must have.
Does anyone know the following information about that particular spring :

  • outide diameter of the wider end
  • outside diameter of the narrower end
  • inside diameter of the narrower end
  • overall height of the uncompressed spring
    I have looked at the McMaster-Carr website and they have loads of conical springs. I might be able to find one there once I know the proper size needed
    Thank you very much for your help

The spring is listed in the Mark VII SPC as Jaguar part 1648 or SU part 3146
If you are in France, I don’t think McMaster will deal with you. They won’t with the UK and Australia.
You can make it from .020" spring wire or a guitar string
4 coils, overall length about .625"
The smallest coil is about .25" diameter or smaller than the plunger shaft so it is captured at the swivel and doesn’t get away from you.
The largest coil is about .85" diameter or smaller than the solenoid body.
The flared brass washer sort of constrains the upper end of the spring. I don’t see it listed separately in any of the SPCs in my library.
There is a fiber washer in there as an air seal.
1.108" OD x .882" ID x .035" thick

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Thank you so much for your prompt answer.
I am in France only in the summer. The rest of the time, I keep my old bones warm in Florida where the XK120 resides too, so it shouldn’t be a problem to order from McMaster-Carr.
I appreciate you sending me the info I was looking for and it was news to me to learn about the fiber washer, which makes sense, but I would never have guessed it. This forum is a treasure trove of information.

Bernard, quick question- how did you achieve that finish on your carb? Media blasting or paint?

Media blasting is very ‘yesterdays’ method, and being abrasive was never a good method anyway… best to chemically clean which is sufficient (use a special purpose aluminium cleaner, such as from Loctite and many similar others) or if you want a non-abrasive ‘show’ finish Hydro-blasting (or under various similar names, like aqua blasting). But definately not paint…

Bonjour Bernard,

I had a look at the original SU catalogue section AUC 9580 which described the H6 Thermo carburetters (in proper English) for the Jaguar XK 120 and XK 140.

SU doesn’t list (nor shows) the “flared brass washer” at all in their catalogue. See the pictures below. You can zoom-in for details.

I don’t know whether this brass washer was initially a part of the Solenoid (69) or a (much) later addition. SU also refers to this as the “Solenoid assembly” and in the later XK 150 documents even Plunger AUC 8179 and Conical Spring AUC 3146 are no longer mentioned as separate items. So the brass washer was probably part of this assembly.

A new Spring AUC 3146 is still available on eBay Australia but shipment is 5x the price of the item.

Bonne chance Bernard et salutations,

Bob K.

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Burlen seem to have the spring in the UK:

No photo, but the number’s correct.

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BTW the draftsman who made the drawing in the XK120 SPC drew the spring upside down.

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75? I think the wide end should go towards the brass washer/solenoid?

No, the spring D54 is upside down.
He got it right on AD57.

I understand there’s an early solenoid assembly AUC 8177 and a later version coded AUD 9490 with Lucar connection. See the one presently on offer at eBay USA
I haven’t checked yet when the later version was introduced but that version came with the flared brass washer.

Bob K.

The carb on the picture is not mine. I used that picture for illustration purpose only. The car belongs to Peter at xk140.nl. You may be able to contact him through his site. I achieved a very similar finish with the help of a set of 3 little hand brushes from Harbor Freight ($2 and change) I started with the steel brush to remove the caked dirt, then used the brass brush for a nicer, natural finish and finally used the nylon brush which gave the metal a nice sheen. It is a lot of work though, but I didn’t mind since I did not want to use any kind of media blasting, as I am afraid there always will be some media left somewhere to ruin your parts later on.

I agree with you. Blasting, as quick as it may be, never gives you back the original appearance of a part. My purpose is to clean parts, not to change their appearance for what is (in my opinion) an over-restored look. Carbs were never that pretty in the first place, and there are sometimes slight variations of color on the same carb body. Some of us can live with it, some of us can’t. I take notice of your cleaning method and will try the chemical approach as I am far from being done with my carb project. Thanks

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Bonjour Bob,
Thank you for taking the time to research that matter. I am familiar with the drawing you posted. As I mentioned to Rob in my first posting, I suspected there is an early version of the set-up which didn’t have the flared brass washer, which seems to be confirmed by the drawing from SU. I saw somewhere that this washer was added for the XK140, but I can’t remember where I read that. I am sure the washer was added for a purpose (probably added reliability) and I would like to have it. I will look up the spring on Ebay Australia .
Merci et a bientot.

Thank you so much for locating the spring. I did look up the Burlen website which I am familiar with but failed to see this item listed. I need a few other items from Burlen so this is great news

Absolutely, it is amazing that you spotted it. Another SPC error to add to the list !

As a matter of curiosity, I looked up the XK140 and XK150 spare part catalogues, but none of them lists either the spring or the washer as a separate part. The XK140 SPC doesn’t even mention an AUC number for the whole solenoid unit, which adds to the confusion. In the end, I can live without the washer for now since my car probably didn’t have it in the first place, and thanks to Roger King, a source for the spring has now been located.