Twin carb needles

[Marshman 1360]

Been told my needles are worn on my twin su's. The choke isnt working correctly and fuel is not getting thought enough. I have taken out the needle and the code number is ANN this is a 1500 spit engine in my herald, does this seam to be the correct code.

Andy

[CharlieB]

Standard needles for a 1500 (HS4s) are ABT (early) or ADN (late).
AAN are standard for 1300 (HS2s)
I assume ANN is a mistake?

[Clive]

Hmm, which carbs are fitted? HS2/ 1 1/4" or HS4 1 1/2"??
easy way if unsure is the bolts to the manifold, hs2 are at 12 and 6 o'clock, hs4 at about 45degrees.
The 1500tc saloon had hs2 carbs and was fitted with AAX needles (according to http://www.sucarb.co.uk/ExplodedImageClassic.aspx?pumpsearch=&ProductId=10986 )
which are pretty similar to the aan needles http://www.mintylamb.co.uk/suneedle/ is the place to compare!

[Marshman 1360]

Thanks Guys i think that the AAN's are the ones so i will get them ordered and i will let you know if it does the trick

Thanks

Andy

[bxbodger]

SU choke mechanism works by lowering the jet away from the needle, effectively increasing the size of the jet's orifice, it's a mechanical linkage and completely seperate from the needle, so if anything a worn needle will produce over-fuelling on choke rather than underfuelling.

You may need to look elsewhere if you have a choke problem, because it's very unlikely the needles will have anything to do with it.

[Clive]

And add to that needles on biased carbs do not seem to wear. On the earlier carbs (fixed needles, you need to centralise the jets with care) they can wear but at the same time the jets will be worse.
You need to find out what carbs you have fitted. I very much doubt new needles will have any effect.
For what its worth it is also worth trying to blow through the jets, they can get partially blocked. And if you are buying needles to sort a problem, it may (may) be worth investing in new jets too, and possibly spindles (they can cause havoc if badly worn)

[Marshman 1360]

The carbs are twin su but i dont know the exact model. He is replacing the needle and the bit below the needle, he explained it that the worn needle causes a blockage that results in not enough fuel is getting through, when off choke. When choke is out it runs very smooth but splutters when choke is all the way in.

[bxbodger]

He's replacing the needles and jets then, the jet being 'the bit below the needle'.....but a worn needle normally allows too much fuel through rather than not enough, and only then usually in the mid range when driving. A worn needle won't cause a blockage- just the opposite in fact.

If it runs ok with the choke out but not with the choke in, I'd be looking firstly at wether the mixture is set correctly in the first place-not difficult on an SU: they are essentially a very crude but effective piece of kit and easy to sort. It sounds to me as if it's running a bit to lean, but worn needles and jets wouldn't cause this.

[Marshman 1360]

The engine had been stood for 10 years until february this year and has no major work done to get it back on the road. So the needles and jets can be replaced without any guilt. I was wondering if the choke cable and the connection to the bar at the carb is worn or a spring is not working hence the choke not engaging at all unless pulled out completly.