I have been cleaning up twin HS4 SUs and decided to fit new jets. Thought the jets for HS2 and HS4 were the same - allowing for LH and RH differences. Had a spare pair of jets for twin HS2 SUs, so fitted those to the HS4s.
The RH jet (in front of driver AUD9141) fitted well.
The LH jet (passenger side AUD9142) is obviously short and it is preventing the choke movement operating smoothly.



Is the carburetor angle on minis 20 or 30 degrees?
Are HS2 and HS4 the same angle?
Does this explain why some jet tubes are not long enough? Or are aftermarket manufacturers setting their own specifications for these things?

I came across this issue when having the twin HS4's on my SPO41 car rebuilt. Float bowl angle is 30 degrees.

The jets are AUD9102 (LH) and AUD9098 (RH) as you can see in the SU Police HS4 spec sheet and in this Minispares listing.

https://www.minispares.com/product/classic/AUD9102.aspx

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Sorry, can't remember the significance of the three types in this pic, or their part numbers.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Thanks winabbey for the SPO drawing. Very interesting as there isn't much information on SPO in detail.

Thanks also for your comments about the jets being an issue for you too.
Can I suggest you may have the part numbers back to front: according to MS, AUD9102 is RH (driver's side) and AUD 9098 is LH.

At least I know what I need to sort now. Thanks again.

Hey Bill, where did you get the red jets?

Bill - either the SU drawing for the LH carb is wrong or MS is wrong. Sorry, can’t remember what the resolution was with mine. SU didn’t have the equivalent drawing for RH in their archive.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

The red coloured jet is actually in one of winabbey's posts.

I think the red jets indicate a shorter flexible hose as they are all specified for horizontally mounted carburettors where the float bowl is closer to the bottom of the jet than on carburettors that are tilted, like minis.

The drawing you posted is for the RH carb as labelled near the top right hand corner. That carb would be in front of the driver.

The bit I'm suggesting is 'wrong' is the added note in a different typeface: "Jets AUD9102 (LH) / AUD9098 (RH)"

I have been going off the drawing label of LH as shown in the top left margin.

I added the jet numbers in different font to clarify as some parts of the drawing are indistinct.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

winabbey, where did you get the RED jets?

Can't be absolutely certain but pretty sure it was SU Midel.

https://www.sumidel.com/shop/category/jets

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Thank you Bill for raising this intersting question. The answer is quite complicated. There is surprisingly very little in the drawings about exactly what the carburetter angle is for these carburetters. Contrary to what I have written in my books (20 deg), I am convinced now that all the carburetters (except for Mini Matic) are 30 degrees and this is consistent with the various manifolds used as well. However, the reason why 20 degrees has crept in is because some parts books specify a jet which is supposed to be fitted to a 20 degree carburetter even though they are used, in our case, in 30 deg units. In one case, one parts book for a Cooper as having a 20 deg jet on one side and 30 deg on the other side!. So what's the difference?

Bill is right to say that the tube length is the only difference. For jets AUD9141/AUD9142, the tube length is 3.33" and is supposed to be fitted toa 20 deg carb. For jets AUD9098/AUD9102 the tube length is a little longer at 3.425" and is supposed to be fitted to a 30 deg carb.

Often parts books specify TK6000 which I believe is a Warneford locally made jst which is presumed to have the longer tube. The genuine SU jets are black. For Mini matic, the jet is red, and this signifies fitment to a horizontal carburetter.

Parts books mix all these up regularly. For ex, for an 850, jet AUD9141 is specified but this is for a 20 deg carb where the float bowl (often the only drawing which actually shows the angle involved) is actually 30 deg. regards, Tony

I should have mentioned that the pic of my carbies with the red jet was during the test fitting stage. Pretty sure it has a black jet now.

I came across SU Midel invoices for parts AUD9148 and CRK147. The jet tube now fitted would have been one of those I reckon. I'll get a pic of the final assembly when next near the car (could be a while).

This is the setup before disassembling for refurbishment.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

I’m thinking jets for the MGB may be the right ones as they are twin HS4’s, although with 20 degree float bowls.

The parts fiche says they are both part TK6000, but SU publications show AUD9141 (Front) and AUD9142 (Rear).

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

An old Midel catalogue lists AUD9148 as RH jet for HS6 to suit 30 degree angle but with 0.10 inch jet diameter (not 0.09) and fitted to Morris Marina 1.8 litre. No carby part number listing of CRK147.

The jets in your 2 photos are a universal fitment (not handed) type. The flexible tube and sleeve are much larger than 'genuine' SUs and slightly longer.

Various MG-B models in different markets used one or the other HS2 Cooper S jets but rarely together as a pair.