Amal needle question...

My notes say that 4-ring needles are for use with a cutaway spray tube and the 2-ring needle is used with the flat top spray tube.

Can someone verify this and are the two types practically interchangeable?

Note that the 4-ring is longer than the 2-ring.

Bob Z. said:

My notes say that 4-ring needles are for use with a cutaway spray tube and the 2-ring needle is used with the flat top spray tube.

Can someone verify this and are the two types practically interchangeable?

Click to expand...

The 4 ring needle and stepped spray tube combination was certainly used on 850 models.

There has been some past discussion about whether the 4 ring needles and stepped spray tubes were fited to all 850s or only the noise reduction "A" models, however, there doesn't appear to be any evidence in the '73-'74 850 parts lists to support the idea that the 2 ring needles and flat spray tubes were actually fitted to any 850 models.

I believe my Mk2a had cut away and 2 step needle. I installed new 3 step needle and it seems to work fine, except my left hand carb is running out of fuel at high RPM, but I think that is another issue. Gonna check my float.

jamesp said:

I believe my Mk2a had cut away and 2 step needle. I installed new 3 step needle and it seems to work fine, except my left hand carb is running out of fuel at high RPM, but I think that is another issue.

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I'm not sure exactly what you mean by 2 & 3 "step" needles? Do you mean the taper?

The Amal needles normally have three grooves but the standard 4 stroke needle used with the flat spray tube has 2 ID rings above the circlip grooves and the needle for the stepped spray tube has 4 rings.
http://www.amalcarb.co.uk/TechnicalDetail.aspx?id=11

Markings
Where used
Part No:

1 inscribed ring
2 Stoke, 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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Excellent info, the needle photo is very informative.

A bit of follow-up:
My 1972 750 had always run rich with a dry sooty black spark plug, but good starting and throttle response.
The accumulated carbon soot was easy enough to wash off the plug after fouling symptoms made starting more difficult.

I checked and it had the 4-ring needles in it. I suppose I had in the past thought that the longer 4-ring needle meant a leaner
mixture due to it sitting lower in the jet holder. Not so; apparently the 4-ring was designed to allow a richer mixture for the larger
850 engines.
My 750 has 32mm Amals with flat top spray tubes.

I experimented and replaced with the 2-ring needles and after a quick test run did a plug check and saw a better looking
dark brown color on the plug.

By the way, I have a 1975 Mk3 sitting in storage that has the cutaway spray tubes in its Amals.
I bet I know where I got those 4-ring needles from long ago!

Bottom line is: use the 4-ring with cutaway spray tubes and the 2-ring with flat tops.

"I'm not sure exactly what you mean by 2 & 3 "step" needles? Do you mean the taper? "

I meant grooves for adjusting needle height in the jet. As I said before, my Mk2a had needles with two grooves for adjustment with cut away. Counter person at Rabers said he thought the bikes that came stock with the black cap mufflers had less adjustment options, thus the two grooves.

jamesp said:

"I'm not sure exactly what you mean by 2 & 3 "step" needles? Do you mean the taper? "

I meant grooves for adjusting needle height in the jet. As I said before, my Mk2a had needles with two grooves for adjustment with cut away. Counter person at Rabers said he thought the bikes that came stock with the black cap mufflers had less adjustment options, thus the two grooves.

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Which 3 groove needles did Rabers sell you, as the stepped spray tubes should use the 928/104, 4 ring needles?

2 groove needles sounds unusual. Do they have any markings?

Anyone else found needles with only 2 circlip grooves in their Commando's carbs?

My october 73 850 cam with 4 inscribed rings 3 neddle clip ajustment grooves and a cutaway spray tube

Phil

I dug out my old needles and see that I erred. They have 4 rings and 3 adjustment grooves. They sold me 622/124 as replacements.

Just checked a photo of my 850 MkIIA carbs when they were stripped, and the needles are 4-groove.
They definitely have 3 clip grooves too :wink:

jamesp said:

I dug out my old needles and see that I erred. They have 4 rings and 3 adjustment grooves. They sold me 622/124 as replacements.

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If you are now running the 2-ring needles with the cutaway spray tubes, have you noticed a change in performance and plug color?

"If you are now running the 2-ring needles with the cutaway spray tubes, have you noticed a change in performance and plug color?"

I haven't been able to do much riding since I went through the carbs. It idles much better and mid-range feels good. My left hand carb seems to be running out of gas at high RPM when I jump on it. I need to resolve that problem before I can give much feedback.

"If you are now running the 2-ring needles with the cutaway spray tubes, have you noticed a change in performance and plug color?"

I checked my plugs today after about a 20 mile ride. They are black around the base of the threads and slightly lighter on the tip/electrode. Seems I should back off to the middle needle setting, at least. I still have an app. 5500 rpm misfire when I'm on it. I have checked my floats and they are fine, tickle right up. I'm wondering if I should go back to my original needles, or if its an electrical problem? My local Norton guru suggested I clean the kill button and ignition switch for built up carbon.

Bob Z. said:

My notes say that 4-ring needles are for use with a cutaway spray tube and the 2-ring needle is used with the flat top spray tube.

Can someone verify this and are the two types practically interchangeable?

Note that the 4-ring is longer than the 2-ring.

Click to expand...

The above statement is correct and they are not interchangeable. I just found out the hard way after being sold the wrong needles for my Amal rebuild.