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HS1 SU Carburettor
I have what I understand to be a HS1 SU carburettor which is missing the dashpot, damper, spring and plunger. Does anyone know whether these parts from the later HS2 will fit? They seem to come up on Ebay more often.


isn't the HS2 an inch and a quarter?
I think I had an 1 1/8" later dashpot that fitted an 1" SU, but needed some rubbing down around the mating edge to properly fit.
Try the Burlen website it is full of exploded diagrams and part numbers.
Thank you for the replies. I have just looked at the carburettor again. The float chamber has a tag on it saying AUC 912. It has 1.25" choke, larger than I had realised.

AUC 912 is off an 850 Mini I believe. 
A 1 1/4" SU will go quite well on an A7 with the right needle and spring in it.
They are fairly cheaply picked up at autojumbles etc if you don't mind a bit of cleaning. New spares will cost an arm and a leg by comparison.
Chris. That is good to hear. I have seen quite a few 1.25" carburettors on eBay and they are not selling. It should prove much easier to get the missing parts for this carburettor than the carburettor that I thought that I had


Is HS1 a semi downdraught? The horizontal carbs look far more period on a non special. The 1 and 1 1/8 horiz carbs seem to differ only in the output bore. I dunno at what size the internal aperture and the suction assembly differ.
I agree the earlier ones look better Bob.

It's still not too hard to find a grubby 1 1/4" for £25 or so. The one on my car was £1 in a jumble sale. I'm going on memory but I think it has an AN needle & red spring; which is probably not optimal by a long chalk  but runs OK!
I think there is a bit of confusion here.

There never was an HS1 SU - The HS range started at 1 1/4" HS2, as used on Minis, Minors 1100's etc.

There was an H1 which was an 1 1/8" SU that could be either horizontal or semi Downdraught, depending on what float chambers were fitted.  The H series were available in H1 - 1 1/8, H2 - 1 1/4, H4 - 1 1/2, H6 - 1 3/4 & H8 - 2"

Kulled from Wikipedia for ease:

SU carburettors were supplied in several throat sizes in both Imperial (inch) and metric (millimetre) measurement.

The carburettor identification is made by letter prefix which indicates the float type:

"H": introduced in 1937 in which the float bowl has an arm cast into its base, which mounts to the bottom of the carburetor with a hollow bolt or banjo fitting. Fuel passes through the arm into the carburetor body. The bolt attaches to the carburetor body just behind the main jet assembly.

"HD": introduced in 1954 with the float bowl mounted with its arm fastening directly below, and concentric with, the main jet. The arm has a flange that fastens with 4 screws to the bottom of the carburetor, and sealed with a rubber diaphragm integral with the main jet.

"HS": introduced in 1958 the float bowl can be rigidly or rubber mounted to the main body, fuel is transferred by an external flexible pipe to the jet. The jet moves down to richen the mixture for cold starting,when the 'choke' linkage is pulled.

"HIF": (1982) the float bowl is horizontal and integral (hence the name) Horizontal Integral Float."HV" (1929), "OM" and "KIF" types also exist but were less commonly employed.[Only registered and activated users can see the links Click here to register]

The Imperial sizes include 1-1/8", 1-1/4", 1-1/2", 1-3/4", 1-7/8", and 2", although not every type (H, HD, HS, HIF) was offered in every size.  There were also H models made in 2-1/4" and 2-1/2", now obsolete. Special purpose-built carburetors (Norman) were made as large as 3".

To determine the throat size from the serial number: If the final number (after one, two or three letters, beginning with H) has 1 digit, multiply this number by 1/8", then add 1". For example, if the serial number is HS6, the final number is 6: 6/8 = 3/4", add 1, total is 1-3/4", etc.

If the final number has 2 digits, it is the throat size in mm. For example, if the serial number is HIF38, the final number is 38, size is 38 mm etc.

Before the H, HS etc. There were the OM range, which were also either semi downdraught of horizontal depending on the float chamber employed.  & were most commonly a 1" size.

In my opinion you can get away with an H series on a 7, but an HS series looks totally out of place as it is nearly 30 years to young for the application.

Lots of good info on the burlen fuel systems site.  [Only registered and activated users can see the links Click here to register]
Agree with what Mark says.

From the left:

1" Side Draught OM, 1 1/8" Semi Downdraught H1 (with T2 float Chamber rather than T1), 1 1/4" Semi Downdraught HS2.



And this is the list of SU types from the Burlen Catalogue



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