Best needle for a SU HS4 carb?

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jagnut66
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Best needle for a SU HS4 carb?

Post by jagnut66 »

Hi,
Please can someone advise what is the best needle size to fit into a SU HS4 carb, when running it with a 1098 engine?
The carb in question is ex-Marina, so the needle in it will have been matched to a 1300 engine originally.
Many thanks,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
philthehill
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Re: Best needle for a SU HS4 carb?

Post by philthehill »

Try a No: 6 needle with red spring.

jagnut66
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Re: Best needle for a SU HS4 carb?

Post by jagnut66 »

Found this site:
https://www.7ent.com/pages/articles-tec ... eedle.html
Scrolled down to Single HS4 1.5", tenth line down is '1098 Std', the next column is 'Needle Std' which quotes type 'CZ'.
This is followed by two other columns, Needle Rich and Needle Lean. I think standard is what I need though.
Anyone?
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
jagnut66
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Re: Best needle for a SU HS4 carb?

Post by jagnut66 »

Try a No: 6 needle with red spring.
Noted Phil, thanks.
What's the difference between a red spring and the black spring I have at present?
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
philthehill
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Re: Best needle for a SU HS4 carb?

Post by philthehill »

The spring rate or strength of the spring.

kevin s
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Re: Best needle for a SU HS4 carb?

Post by kevin s »

Have you tried it with the std 1300 set up you have? In my experience it will run fine. When setting up an SU you choose the spring to ensure the piston full travel is used (to stiff a spring and it would only half open, to weak and it would be at max lift before engine achieves peak airflow so you would lose control of the fuelling) you then choose a needle to give you the fuelling you need for the airflow at each point of piston lift. So your 1300 set up may not fully lift the piston and you could go to a slightly weaker spring and corresponding needle as Phil suggests, as it is it will still give the right mixture though just not the maximum possible power. That said if you have other tuning mods such as a better exhaust , head and cam the engine may well be flowing similar air to a 1300 anyway.

The biggest issue I have seen with probably 70% of the SU's I have worked on is worn jets, if they are even slightly worn you will never get it to run right, changing them for £20 or so usually transforms a car. I think modern fuels may make the wear worse as well.
jagnut66
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Re: Best needle for a SU HS4 carb?

Post by jagnut66 »

The biggest issue I have seen with probably 70% of the SU's I have worked on is worn jets
It has a new black coloured jet on it, to replace the worn old wax stat it came with. The problem I have at present is that the engine runs way too fast, no matter how I try to adjust the carb (or distributor), so I'm hoping a correct 1098 sized needle enable me to will cure this. It should arrive today, so we'll soon know.
If not I'm giving serious thought to refitting the original HS2 carb, which it ran fine on, before I fitted the new exhaust.
That will mean drilling a couple of holes in the Maniflow mounting plate to fit it but I believe this will be doable and won't stop me trying another (different) HS4 at a later date.
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
jagnut66
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Joined: Fri Apr 11, 2008 7:28 pm
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Re: Best needle for a SU HS4 carb?

Post by jagnut66 »

The new needle has arrived but before I try it I thought I'd stop for a cuppa...........
I have replaced it in the carb though and put that back together.
The needle in it was an 'EB', which is listed on the site I posted a link to (earlier post on this) as one for a 850 / 998 Mini engine.....
Starting to wonder if the adjustment screw on the carb is actually doing anything......
So I'm not holding my breath and the drill is on standby..... :wink:
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
kevin s
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Re: Best needle for a SU HS4 carb?

Post by kevin s »

if it's running to fast changing the jetting won't help, you have air leaking past the throttle plate somewhere, you should be able to close it down to the point the engine stalls on the adjustment screw.

Does the throttle plate have a little sprung loaded valve in it, if so as they age the spring loses tension and lets air past, ideally replace with a flat plate or at a push araldite the valve shut.

if not it could be a worn throttle spindle or something in the linkage stopping is shutting fully.
jagnut66
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Re: Best needle for a SU HS4 carb?

Post by jagnut66 »

That was part of the problem, the adjustment screw wasn't doing anything.
You are right, my forlorn hope that the replacement needle would make a difference, was just that.............
So I had a root through my spares and found I have another HS4 (probably also ex-Marina) hidden away, however this one had a leaky jet, which no amount of tightening would fix...........
So I swapped it for the non-leaking new one on my problem carb.
I don't know if this HS4 will be any good because guess what, after replacing the leaky jet with the new one, this also leaked :roll: ...........
I don't have a spare jet.
Thoroughly fed up by this point, plus having found that the Maniflow mounting plate was pre-drilled to suit the HS2 as well, I have reattached this to the car.
It doesn't leak.
However it is too late to try starting her up tonight, can't be that cruel to my neighbours :wink: , so testing will happen tomorrow morning.
At this point, she either works or stays at home, whilst I take Hetty the Triumph to the Morris Register Rally.............
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
jagnut66
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Posts: 3635
Joined: Fri Apr 11, 2008 7:28 pm
Location: Mansfield, Nottinghamshire.
MMOC Member: Yes

Re: Best needle for a SU HS4 carb?

Post by jagnut66 »

Well Elsie May delivered me to and from the Morris Register rally without anything major occurring. :D
Hopefully she'll do the same tomorrow, then I can spend the week servicing Hetty the Herald in advance of the joint Triumph / MG rally next weekend.
Fingers crossed and touching wood.
It's nice to actually drive a Morris again.
I will revisit the HS4's when I decide to let them out of the dog house....... :wink:
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
minijojo
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Re: Best needle for a SU HS4 carb?

Post by minijojo »

i have a HS4 installed on my 1098 engine. It is a FZX1160 with an ADF needle installed. I guess with a black spring. I am not satisfied with the gas acceptance in the partial load range, so i wanted to tryout Phils proposal.
I have no problem finding a red spring for the HS4 carb, but sorry for my question, i don´t find a "number 6 needle" for my HS4 carb witch is a spring needle guide fixing typ. No 6 needles i only found for fixed needle guide.
can someone give me an advice please?
regards
Joachim
minijojo
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Re: Best needle for a SU HS4 carb?

Post by minijojo »

just installed the red spring and a needle ABJ (standard for HS4 on a 1098) to my HS4 (bias type) carb. Now it is running much better in all ranges
thanks to all for the tips and hints
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