amal concentric

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baz

baz

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today i came across a pair of mk 1 concentrics that i bought brand new from a norton dealer for my 750 commando over 15 years ago , i was never happy with how they worked they were no better than my old worn out ones i just chucked them in a box in disgust went back to my old ones then later on a single mikuni ,i took the carbs to bits today they are 32mm with 230 mains 106 needle jet a 4 ring needle but without a sectioned spray tube ,the spray tubes fitted are the square top type! surely this needs a 2 ring needle? also they are fitted with number 3 cutaway slides! this is how they were set up and sold to me all those years ago has anyone seen 750 commando carbs set up like this? cheers baz
 
Except for the jet needles being 850 type sounds like these are set up for a '72 combat engine
 
And the parts book does say that those needles should be used with the stepped spray tubes ...
 
Roy Bacon's Norton Twin Restoration has a 73 combat Page 227: R932/26 L932/27 for 230 mains, #3 slide, 32MM, pos 1 on the needle,106 needle jet.
you may as illf8ed stated have 850 needles from your description. They are longer than a 750 needle type. Put a vernier caliper on the needle length. My 850 needle (4 mark ring identifier) is: 2.765" my 750 needle length (2 mark rings identifier) is: 2.6695" What is on the embossed oval just below the 932 stamp?
Cheers,
Thomas
CNN
 
definitely the wrong needles then! i think i will try some 2 ring needles in there and maybe some 3 1/2 slides and give them a try cheers
 
Baz
baz said:
definitely the wrong needles then! i think i will try some 2 ring needles in there and maybe some 3 1/2 slides and give them a try cheers
Click to expand...
ok re read it you have a 750. which should have a #3 slide.
Cheers,
Thomas
CNN
 
CanukNortonNut said:
Baz
baz said:
definitely the wrong needles then! i think i will try some 2 ring needles in there and maybe some 3 1/2 slides and give them a try cheers
Click to expand...
ok re read it you have a 750. which should have a #3 slide.
Cheers,
Thomas
CNN
Click to expand...
oh ok i thought you meant only the combat had a 3 cutaway , cheers
 
CanukNortonNut said:
Roy Bacon's Norton Twin Restoration has a 73 combat Page 227: R932/26 L932/27 for 230 mains, #3 slide, 32MM, pos 1 on the needle,106 needle jet.
you may as illf8ed stated have 850 needles from your description. They are longer than a 750 needle type. Put a vernier caliper on the needle length. My 850 needle (4 mark ring identifier) is: 2.765" my 750 needle length (2 mark rings identifier) is: 2.6695" What is on the embossed oval just below the 932 stamp?
Cheers,
Thomas
CNN
Click to expand...
on the embossed oval it has l301 on the left and r300 stamped on right carb cheers
 
baz said:
CanukNortonNut said:
Roy Bacon's Norton Twin Restoration has a 73 combat Page 227: R932/26 L932/27 for 230 mains, #3 slide, 32MM, pos 1 on the needle,106 needle jet.
you may as illf8ed stated have 850 needles from your description. They are longer than a 750 needle type. Put a vernier caliper on the needle length. My 850 needle (4 mark ring identifier) is: 2.765" my 750 needle length (2 mark rings identifier) is: 2.6695" What is on the embossed oval just below the 932 stamp?
Cheers,
Thomas
CNN
Click to expand...
on the embossed oval it has l301 on the left and r300 stamped on right carb cheers
Click to expand...
Ok Baz
in the Roy Bacon book that I have
R930/30 and R930/31 is for a 69 750 Size is 30 mm, jetted with a 220 main, #3 slide, second position needle and .106 needle jet.
That's what is described.
The 230 mains that you have may still be ok. Check that on the uphill WOT plug chop.
Just get a new set of needles and give that a go.
Cheers,
Thomas
CNN
 
L.A.B. said:
baz said:
on the embossed oval it has l301 on the left and r300 stamped on right carb cheers
Click to expand...


http://amalcarb.co.uk/rh-32mm-4-stroke- ... ettor.html
http://amalcarb.co.uk/lh-32mm-4-stroke- ... ettor.html
This carburettor is built to a standard specification which provides approximate settings for this bore size and carburettor type. Ideal for anyone who wants to tune their machine themselves.
Click to expand...
Click to expand...
there you go L.A.B. knows where to look. Don't mind me... :roll: So now Baz, is your bike a Combat or a standard 750?
Thanks.
Cheers
Thomas
CNN
 
CanukNortonNut said:
L.A.B. said:
baz said:
on the embossed oval it has l301 on the left and r300 stamped on right carb cheers
Click to expand...


http://amalcarb.co.uk/rh-32mm-4-stroke- ... ettor.html
http://amalcarb.co.uk/lh-32mm-4-stroke- ... ettor.html
This carburettor is built to a standard specification which provides approximate settings for this bore size and carburettor type. Ideal for anyone who wants to tune their machine themselves.
Click to expand...
Click to expand...
there you go L.A.B. knows where to look. Don't mind me... :roll:
Thanks.
Cheers
Thomas
CNN
Click to expand...
ha ha you have been most helpful i wonder if LAB knows how the 4 ring needles got in there??
 
baz said:
I wonder if LAB knows how the 4 ring needles got in there??
Click to expand...

Well, as you said you bought them new from a Norton dealer, I expect that's who it was.
 
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