Correct atlas carbs

hillbone

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Gidday.
I have a 1966 atlas and would like to fit the right twin carb set. The Roy bacon book says a 389/241 and a 689/241.
I assume that's a left and right?....are these mono blocks?
Also has anyone a photo of the right headlight switch, amp and headlight setup? I haven't found a photo of a 1966 yet.
Cheers hillbilly.
 
They are Monoblocs. The 689 is essentially a mirror image of a 389, i.e. the float bowl is on the other side. You can still buy new 389's but sadly can't buy new 689's. They do appear on Ebay etc sometimes but it's pot luck if they are any good. However the monoblocs can be sleeved if badly worn & last much better than concentrics do.

Ian
 
My Norton Owners Manual Publication P106/P lists for the 750 Atlas and Scrambler the following data: (No publication date is listed)

Twin carbs:
Monobloc type 389/88 RH
389/87 LH

Main Jet 350
Needle Jet 106
Pilot jet 20
Throttle valve 3

Needle taper D
Needle position 3

Single carb:

Monobloc type 376/294

The remaining data is 400, 106, 20, 3 1/2, C, and 4 respectively.


I hope this helps.
 
About a third of the way through the 1967 model year, beginning just after serial number 121000, Norton switched to concentrics and distributors.

Every P11 came with concentrics, along with late Atlases, N15s and G15s.

It may not be correct for your bike, but concentrics won't really look out of place

Here's a pic of my G15 carbs with the air cleaner mounting plate installed. The cleaner itself is a wedge-shaped contraption that I've also seen on Atlases

Correct atlas carbs
 
I believe that at the same time that the carbs changed to concentrics Norton also changed from mag to points, so if your Atlas has mag ignition I believe it should have the 389/689 monoblocs.
Al
 
If you have access to Roy Bacons Norton Twin Restoration there are some very good period pictures showing headlight and instruments etc, I used this book extensively when I rebuilt my 650SS.
Al
 
possm said:
I believe that at the same time that the carbs changed to concentrics Norton also changed from mag to points, so if your Atlas has mag ignition I believe it should have the 389/689 monoblocs.
Al
Click to expand...

Yes, that's correct. When Norton moved from Magneto to Distributor, they also moved from the monoblocs to concentrics. If the Atlas motor has flat top pistons, then the concentric settings would be the same as the early Commando.
 
Thanks every body. I haven,t been able to respond this week. Appreciate all the info. I,d like to use mono blocs as they look period.
Cheers hilbone
 
Thanks every body. I haven,t been able to respond this week. Appreciate all the info. I,d like to use mono blocs as they look period.
Cheers hilbone
 
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