Different slide needle tips?

I have two Amal Premier carbs with two groove marking needles in (as supplied) i noticed that one of the small ends of the needle is blunt and flat but the other is pointed like a drill bit. Other than that they appear identical.
Then i read on old britts or somewhere (i forget) that there is a two stroke needle that has two marking grooves.
I have checked jets they are four stroke type but the carbs did have different pilot jets that didn't help tick over.
There is one exhaust bluer than the other and no air leak etc. So am inclined to now suspect the needles.
I have a ham can air filter 3 1/2 slides none cut spray tubes 106 needle jets 280 mains a Mick Hemmings big valve head and PW3 cam with straight through pea shooters an none balance pipes. Should i get a new pair of needles which type should i get 2 or 4 marking groove type???

All the info on needles can be found here
http://www.tioc.org/amalbritbike.pdf
Scroll through it and you will eventaully come to some pictures of the needles.
Two ring is the standard used in 750's
Four ring was used in the 850's, it has a different length and taper.
What notch is the needle clip in? Lowering the needle (putting the clip in a higher needle notch) leans the mixture. Raising the needle (using a lower needle notch) richens the mixture.

In any case, the needles should match.

They are on middle notch at the moment but i have made my mind up that i will get a new PAIR. I have seen the four groove type referred to as "lean" and that made me thing given the fact my bike is not a standard 850 (forgot to mention that) i may be better off with two groove type but i don't really know much about the black art of needle selection

Unfortunately Danno the link to the pdf you recommend will not open. Well not for me but i have less luck with the Internet the i do with carbs

toppy said:

Unfortunately Danno the link to the pdf you recommend will not open. Well not for me but i have less luck with the Internet the i do with carbs

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What link?

What spray tube type do you have? The 4 ring needles go with the cutaway spray tubes used on the 850's. The 2 ring go with the standard flat top spray tube.

htown16 said:

What spray tube type do you have? The 4 ring needles go with the cutaway spray tubes used on the 850's. The 2 ring go with the standard flat top spray tube.

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I have standard flat top spray tubes which is why I thought I would need 2 i.d. groove needles

The needle jets and the needles are the items which affect your bike's performance the most as far as carburation is concerned. So it is worth the effort in getting them correct for the fuel you are using. I have two Mk2 Amals on my 850 motor using methanol fuel. I use Mikuni needles because of the variations in needle taper shape which are available. If you are choosing between needles with two groves and those with four, I would always choose the ones with four grooves. However the important thing is the shape of the taper. The needles and needle jets affect the carburation from 1/4 throttle to 3/4 throttle which is the bit you use when riding around corners and making gear changes. The slightest bit of over-rich will take the edge off your motor and if you end up too lean, the bike would cough when you are changing gear.
You should not have the situation there one needle is blunt and the other one is pointed - sounds as though the carbs were second-hand and came off different bikes, so I'd check the needle jet sizes.
I've mentioned that I use methanol fuel - if you are using petrol, it is much more critical to get the needles right, because the jets are about half the size and petrol is much less forgiving of jetting errors.

acotrel said:

If you are choosing between needles with two groves and those with four, I would always choose the ones with four grooves.

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Do you know the difference between needle ID rings and notches for the needle clip?

Or is there something else, called "groves?"

By 'grooves', I mean the bit where the clips fit to raise or lower the needles when tuning. Most needles I've ever seen have had a number stamped on them up near the top. If you have a look at a few 70s Japanese bikes, each model has different needles to suit the motor characteristics. Most use Mikuni type carbs which have a much greater variety of tapers than Amal carbs. This probably doesn't matter on an old dunger such as a commando because the changes in throttle response in most situations goes un-noticed by the rider. If you are looking for best performance, I'd be trying different tapers.

acotrel said:

By 'grooves', I mean the bit where the clips fit to raise or lower the needles when tuning.

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However, the "grooves" in this instance are the identification rings at the top of Amal needles, as both the '2-ring' and '4-ring' Amal needles have 3 clip grooves.

http://amalcarb.co.uk/rebuilding-mark-1 ... arburetter

Markings Where used Part No:
1 inscribed ring 2 Stroke, 600 Series 622/063
2 inscribed rings or 'U1' 4 Stroke, 600/900 Series 622/124
3 inscribed rings or 'X' 2 Stroke, 900 Series 928/063
4 inscribed rings Norton 850, Triumph 250cc 928/104
5 inscribed rings Triumph T160 622/278
Y Alcohol, 600 Series 622/099
Z Alcohol, 900 Series 928/099

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So Acotrel, the reply you have given refers to Mk2 Amals, Mikuni needles and you state that you run on methanol, getting a bit off topic here.

The only difference between using methanol and petrol is the size of the jets and possibly a slightly different taper needles. With methanol you have more margin for error, however if you are looking for best performance, it is as difficult to tune as with petrol. The problem is the same. If you use jets small enough to make the motor cough when changing gear then raise the needles one notch, you get the bike to behave with sanity. Then getting the right taper is a different problem. Especially with petrol, the slightest bit rich will always take the edge off the motor. Getting the jetting right in the range from1/4 throttle to 3/4 throttle opening is extremely important, and that is what the taper affects. As you come out of tight corners and wind the throttle on the slightest bit of richness will make the motor sluggish - particularly with petrol. It takes a lot of stuffing around changing needles and jets, however it is worth the effort. With methanol fuel, you have much more leeway for error. When you get it right, you will know the difference.
Incidentally, relying on plug readings only works when you are changing main jets, and when you fine tune your carburation, you have to watch the weather - cold weather will effectively make the jetting leaner and can cause damage if you are running near the limit. I always use main jets which are slightly too rich.

I never use Amal needles, Mikuni needles for the same size carburettor give a much greater choice of tapers, and the diameter of the parallel part of the needles and distance from the centre groove to the shoulder of the taper are the same. If you start with the clip in the centre groove, the motor should start and run and when hot, it should not spit back through the carb. When you ride the bike, if the clips on the needles are in the centre groove, it should not cough when changing gear in corners, - however If you lower the needle one notch , it SHOULD cough. The rest is about judging which taper needles give you the best acceleration coming out of corners, when the clip is in the centre groove. If you use main jets one size larger than recommended by the manufacturer of the motor, you should stay safe and not do any damage.
You will note that my comments are all about tuning mid-throttle - most bikes don't stay on the main jets for long, and if they are slightly rich, you will stay out of trouble.

toppy.
To simplify. If you have carbs with non- cutaway spray tubes you need the two ring needles . They are .817" long and they should be identical. That is fact, not opinion.

If you have carbs with a cutaway in the spray tube, whether they find their way on 850's, 750's, Triumphs, or anything else, they need 4 ring needles. These needles are .892" long. This also is fact, not opinion. You can not mix and match needles and spray tube styles.

Sounds like you do have a mixed pair of carbs, but by assuring all the internals are identical; main jets, needle jets, spray tube and metering needles, as well as slide cut number, you have essentially built yourself a matching set. No one can advise you to which of the three needle grooves will work best for you because few of our engines are identical.

Thanks Biscuit. I have ordered new 2 id groove needles and 106 needle jets. The carbs have flat top spray tubes and where both new bought premieres all internals matching. The issue is that one of the needles has flat or blunt small end but the other has a point much like a drill bit. I can't see any other difference between them but don't trust them to be a matching pair so will change them and their jet. They have covered about 3000 miles from new and the bike is running well but bluing of the exhaust on one side is more than the other even though the carbs are balanced and engine fires equally. It may well make no difference but its a peace of mind thing.

The easy answer is always to use the combination which has been established to work well, however it might not be the optimum for your particular motor. It depends on how you intend to use the bike. If you use it for the Sunday competition up the local winding scenic road - that is a different requirement to simply using the bike as a commuter. In Victoria, the go was always the race up Arthur's Seat which is a high hill near the beach on the Mornington Peninsula - depends on your sense of humour. These days there is usually a cop with a motorbike sitting in the top car park on week-ends .

Being unbalanced, (like myself) makes it a little easier to determine a couple of rudimentary things, since each exhaust pulse exiting the pea-shooter is from one cylinder only without dilution from it's mate.

Holding your palms behind the idling bike, are the pulses equal and the same temp?
Are the exhaust tips showing the same deposits.

If pulses feel equal and sound equal to. Tick over is smooth (well you know what i mean :roll: ) and steady. The new needles and jets arrived today but apart from a visual inspection i have not had chance to fit them or compare with those currently fitted. It forecast rain all weekend so will fit them then.