standard 1 1/4" carb

[estepona1999]

Can someone please answer these questions.
What oil should I use for the dashpot and what sort of quantity
Is the butterfly valve part of the choke,or is that part of the throttle assembly
Sorry for the basic questions but it is over 40 years since I had anything to do with carbs of any sort.
I bought this carb new old stock so it shouldn't be worn.Thankyou in anticipation

[Matt Tomkins]

hi,
Dashpot oil is one of those things that everyone will have an answer, however what Burlen (the makers of SU) sell as carburettor dashpot oil is SAE 30 grade.
And i think youre referring to the brass disc which opens and shuts the throttle ehich is attached through the throttle spindle.
Hope this helps

[philthehill]

Here is the link to Burlen Fuels who are the SU experts

http://sucarb.co.uk/

http://sucarb.co.uk/technical-hs-type-c ... djustments

http://sucarb.co.uk/damper-oil-sae-grade-20.html
(Straight 30 grade oil is more than adequate.)


Follow the links to learn all about the SU carb.

Attached to the float chamber lid is a carb identification tag. Can you please post the letters/numbers (AUC???/AUD??) to confirm that the carb is the right specification for your car.
Minor carb applications details can also be extracted from the following link
http://sucarb.co.uk/cf/vehicle/list/?ma ... icle=Minor

[estepona1999]

Hi Phil,thanks for your reply,I'm afraid the carb doesn't have the tag on it,is that a problem? also what quantity of oil should I put in the dashpot and use sae 30 or can I use 20/50 ? Thanks,Roger

[estepona1999]

Thanks for that Matt,great help

[philthehill]

No tag - no problem.
Just make sure that you have the right needle in the carb which can be deduced from the last link in my post above.
Please let us know what needle you have fitted and what year of Minor and size of engine it is going to be fitted too.
The grade of oil is not that important it is more important that you have oil in the damper otherwise when you press the throttle pedal you may well experience a reluctance for the engine to pick up revs cleanly. 20/50 grade oil will do just fine.
When I ran a single 1.5" H4 SU carb on the Minor I was using EP90 which helped damp the carb piston when the throttle was opened quickly.
Just fill the damper piston cylinder - it will only take a tablespoonful at most. Any excess will drain down and into and be consumed by the engine.

[estepona1999]

I am a total novice nowadays, I bought the new old stock carb from an ad in practical classics,how do I find out the size of the needle.I was told it was perfect for use on my 1958 traveller as I have upgraded to a 1098 cc engine.I will have a look at the link to see the size of needle.

[estepona1999]

I have just looked at the link and it shows 3 different needle jets,weak,standard and rich,how do I know which I should have? thanks,Roger

[philthehill]

The 1.25" HS2 SU carb for the 1098cc engine is the AUD13 type and is fitted as standard with the AN needle.
The needle is secured into the bottom of the piston with a screw. Undo the screw and remove the needle.
The I.D. letters of the needle are stamped on the parallel needle shank where it fits into the piston.
When refitting the needle - the bottom of the parallel shank should be level with the bottom of the piston.

[estepona1999]

Ok,thanks for that,I will try and have a look tomorrow if I am brave enough !! Do I have to remove the carb from the manifold ? I only fitted it yesterday?

[philthehill]

No you do not have to remove the carb - only the piston dash pot (2 screws) (in which the piston rises and falls dependent upon the depression created by the throttle) - that allows you to remove the piston and to gain access to the underside of the piston where you will find the needle screw.
Remove needle and examine for needle details.
Remember to refit the dash pot damper spring.
There is nothing complicated about having to remove the dash pot and piston to examine. Do not even think complicated.
Quite a simple job really.

[estepona1999]

Thanks once again Phil,I will have a look tomorrow,just remind me please as to what we are looking for and I will do my best to find it,cheers Roger

[philthehill]

You are looking for the letters stamped on the needle. Those letters will tell you if you have the correct needle or not.

[estepona1999]

Ok will check tomorrow,what letters should be on it to be correct for my car?

[philthehill]

As stated above - AN needle.

[philthehill]

Duplicate post which I seen unable to delete.

[andypocock]

When I was growing up with cars (and SUs were current fitment) I was taught to fill the dash pots with 3in1. I guess because it was thin and everybody had a can of it. Nowadays I stick pretty much whatever engine oil is to hand in but I always feel a bit guilty as I was taught as a boy that it should be 'thin oil'.

Those were the days. Aerosol cans were for rich people. No WD40 or Plus Gas in my house. 3in1 oil did your bike, door hinges and other squeaks about the house, and dashpots.

The cars and I are growing old together...

[mogbob]

If you want to see a video try Matt Tompkins ( see post above on this thread ) on You Tube . Search "Stripping an SU HS2 carb for rebuild "
It has a section on taking out the needle from the piston. ( A good video Matt )
As stated above you do not need to remove the carb from the engine. Don't loose the little grub screw holding the needle in and note how it is flush to the bottom of the piston before removing it. It may be " grummed in" with old fuel deposits , so a squirt of WD 40 / Plusgas may help removal with a thin, well fitting screwdriver.
Bob

[estepona1999]

Thankyou all.I am going back in the garage now to find out the type of needle.

[estepona1999]

It is stamped what looks like GX,that must mean the wrong needle or is the carb wrong as well?