stepped spray tube and 4 ring needles on Combat?

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Douglass Harroun

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Have a used set of Amals form an 850 with stepped spray tubes and 4 ring needles. Wondering if I can use them on 750 Combat?
Doug
 
Combat Amals are 32mm, I reckon you'd just need to re-jet them to Combat settings.
 
I have an 850 32mms concentric with stepped spray tube and matching needle in a B44 single, works very well but the final main jet is no where near a std B44 size so you will need to find the mains.
 
Call me old fashioned if you will, but if I were looking for carb settings for a 750 combat, I think that as a starting point, I’d probably choose the settings for, well, a 750 Combat...

But that’s jus’ me.
 
Douglass Harroun said:
Have a used set of Amals form an 850 with stepped spray tubes and 4 ring needles. Wondering if I can use them on 750 Combat?
Doug
Click to expand...
I wouldn't worry about the spray tube. Other than the spray tube, a 32mm body is the same for a 750 and 850. If everything else is stock, you need 220 main jets, standard needles, 106 needle jets, and 3 cutaway slides to be standard. If you buy an Amal rebuild kit for each, you'll have the right needles. If they don't need rebuilding, I would give the special needles a try. I have Amal info for Commandos at the bottom of this page: https://www.gregmarsh.com/MC/Norton/CommandoID.aspx
 
I think you need the longer needles with anything other than the flat top spray tubes. It is I believe a safety thing so they don't hang up at WOT.
I run 2 stroke spray tubes and needles one notch lower on my combat, works well. Why, I was experimenting!
 
I ran cut away spray tube 32’s from an 850, but with 3 ring 750 needles, in my Combat for years, worked fine. I just switch the tubes to non cut aways this year, just to try it.

B
 
Interbak said:
I ran cut away spray tube 32’s from an 850, but with 3 ring 750 needles, in my Combat for years, worked fine. I just switch the tubes to non cut aways this year, just to try it.
Click to expand...

Do you mean two-ring 750 needles (622/124 standard 4-stroke) as three-ring (928/063) is a two-stroke needle?

http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter

"Markings Where used Part No:
1 inscribed ring 2 St[r]oke, 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"
 
Yes,

Sorry, the 2 ring needle, 3 clip notches.

B

L.A.B. said:
Do you mean two-ring 750 needles (622/124 standard 4-stroke) as three-ring (928/063) is a two-stroke needle?

http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter

"Markings Where used Part No:
1 inscribed ring 2 St[r]oke, 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"
Click to expand...
 
When I upgraded to Premiers on my Combat a couple of years ago, Surrey Cycles recommended that I had the stepped spray tubes and 4 ring needles. I was pleased that I took that advice, as it made an incredible improvement throughout the range, although that was of course by comparison with the well worn old carbs.
Settings were otherwise standard Combat, 220 mains, 106 needle, 3 slide, with the needle in the middle slot. The carburettors were supplied with 17 pilot jets, but I later found that 19s worked better.
 
snowdr said:
When I upgraded to Premiers on my Combat a couple of years ago, Surrey Cycles recommended that I had the stepped spray tubes and 4 ring needles. I was pleased that I took that advice, as it made an incredible improvement throughout the range, although that was of course by comparison with the well worn old carbs.
Settings were otherwise standard Combat, 220 mains, 106 needle, 3 slide, with the needle in the middle slot. The carburettors were supplied with 17 pilot jets, but I later found that 19s worked better.
Click to expand...

Carbs off a later 850 should work better on a Combat than the standard carbs which were fitted to the Combat. With petrol, the slightest bit rich anywhere takes the edge off performance. British bike manufacturers used to lag behind the Japanese. Virtually every Japanese bike from the 70s had different needle jets and needles, from every other previous model. They fiddled with the tuning to get the best performance. The British were much slower to do that. That is the reason, I use 6D Mikuni needles in my 34mm Mk2 Amals. - I don't trust their Amal tapers when I am trying to lean-off the jetting.
 
There is a very big difference between the way a racing Manx Norton was tuned in the UK in the 50s and 60s, when compared with the way the British tuned the road bikes they sold to the public.
 
acotrel said:
Carbs off a later 850 should work better on a Combat than the standard carbs which were fitted to the Combat. With petrol, the slightest bit rich anywhere takes the edge off performance. British bike manufacturers used to lag behind the Japanese. Virtually every Japanese bike from the 70s had different needle jets and needles, from every other previous model. They fiddled with the tuning to get the best performance. The British were much slower to do that. That is the reason, I use 6D Mikuni needles in my 34mm Mk2 Amals. - I don't trust their Amal tapers when I am trying to lean-off the jetting.
Click to expand...
Don't forget Al he is asking about the stepped cutaway spray tube and 4 ring needles that were fitted only to the 850
The carb itself is still a 32mm MK1 concentric
And don't forget the mikuni VM was designed by Amal
 
acotrel said:
There is a very big difference between the way a racing Manx Norton was tuned in the UK in the 50s and 60s, when compared with the way the British tuned the road bikes they sold to the public.
Click to expand...
Unfortunately the manufacturer just did enough to sell us a bike we'd buy and not much more
 
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