One more Atlas question ....Carbs

texasSlick · Nov 25, 2019

I was at the Harvest Classic rally in Luckenbach last month where I met a fellow, who seemed quite knowlegeable about Dommies and Atlas's.

After I had told him that I was the original owner, he looked my bike over and said "You put dual carbs on it because all 62's had single carbs" (my Atlas is a 62 build titled as a 63).

The question is .... is his statement "all 62's had single carbs" true?

Slick

Peavey Jeltz · Nov 25, 2019

Bacon appears to agree with you. Both "Dominator Twins" and "Twin Restoration" make mention of a single carb for '62. Also Jim Reynolds make a similar note in his "A Racing Legend Norton."

Bodger · Nov 25, 2019

Peavey Jeltz said:
Bacon appears to agree with you. Both "Dominator Twins" and "Twin Restoration" make mention of a single carb for '62. Also Jim Reynolds make a similar note in his "A Racing Legend Norton."

I have a single carb on my '62, but that hardly proves they all came that way.

texasSlick · Nov 26, 2019

I have done an internet search for 1962 sales brochures, in an effort to shed some light on this. None found.
Wikileaks says "....was fitted with a single 376 Amal monobloc", and ... "In 1964 the Atlas was upgraded to 12-volt electrics, and gained a second carburettor and wider fork yokes."

Dunno if I trust Wikileaks .....

FWIW, my Atlas, dispatched from the factory 21 May 1962, showed up at my dealer in April 1963, with dual Amal 389 Monoblocs, a 6 start oil pump, con rod squirt holes, and no model/configuration stamps on the Monoblocs. Do I have a special build?

Slick

mdt-son · Nov 26, 2019

texasSlick said:
FWIW, my Atlas, dispatched from the factory 21 May 1962, showed up at my dealer in April 1963, with dual Amal 389 Monoblocs, a 6 start oil pump, con rod squirt holes, and no model/configuration stamps on the Monoblocs. Do I have a special build?

The 6-start oil pump (NM25396) appears to be a development performed at Bracebridge street. The part number indicates it was developed after the 750 head, thus probably late 1961 / early 62. Series production of the pump didn't commence until 1965 at Plumstead. It seems likely you have a trial sample - maybe your bike was a testbed for future developments? The time spent between dispatch and sale may indicate the bike was used for road testing. Did it have mileage on the odometer?

-Knut

texasSlick · Nov 26, 2019

mdt-son said:
The 6-start oil pump (NM25396) appears to be a development performed at Bracebridge street. The part number indicates it was developed after the 750 head, thus probably late 1961 / early 62. Series production of the pump didn't commence until 1965 at Plumstead. It seems likely you have a trial sample - maybe your bike was a testbed for future developments? The time spent between dispatch and sale may indicate the bike was used for road testing. Did it have mileage on the odometer?

-Knut

It did not have significant mileage .... easy enough to disconnect the speedo cable if it was at Berliner for their evaluation and trials. I rather suspect Berliner had it for all that time, except for transport across the pond. Highly unlikely the dealer would sit for months on a new Norton in a crate, especially as the dealer was a one man show operating out of an old house converted into a storefront. It is possible Berliner lost it in their warehouse for much of that time, but I doubt it in view of the special fitments.

I had a '62 Atlas which I traded for the present one. The first Atlas had a single carb, and was a dog (that is what we called vehicles that did not meet performance expectations). The present one is quick in comparison.

Thanks for your input.

Slick

MikeG · Nov 27, 2019

The Atlas I'm working on now has a single carb, and I'm guessing it's a 63. Serial number is 20-105xxx but I'm not 100% sure of year or originality of anything on it.

texasSlick · Nov 27, 2019

MikeG said:
The Atlas I'm working on now has a single carb, and I'm guessing it's a 63. Serial number is 20-105xxx but I'm not 100% sure of year or originality of anything on it.

That serial # is consistant with a 63

http://classicenglishbikes.com/tech_file/norton.html

Slick

Piefairy · Dec 31, 2019

I bought my 62 atlas and it came with dual carbs. It was from a resto shop in texas. Also
https://www.classic-british-motorcycles.com/norton-atlas.html
seems to indicate there was a bit of a discrepancy on number of carbs on early atlas models.

Bernhard · Jan 1, 2020

My Atlas was ex police which is all I could afford. The single carb downdrought head had 2 dia reducing split collars in the inlet ports , which need to be removed when converting to twin carbs. As it was a 65 model, I upgraded it to double speed oil pump and6 to 12v electrics.

dynodave · Jan 2, 2020

Piefairy said:
seems to indicate there was a bit of a discrepancy on number of carbs on early atlas models.

Piefairy said:
https://www.classic-british-motorcycles.com/norton-atlas.html

Be careful who you think is credible! Can't even identify correctly a BITZA Norton Commando S
https://www.classic-british-motorcycles.com/norton-commando-ss.html
commando "SS"? 850? Mic? disc brake? roadster oil tank?

https://www.classic-british-motorcycles.com/about-us.html

Would you buy a house-car-motorcycle-spark plug from this guy?

Gilesy · Jan 6, 2020

For what it's worth my 1962 Atlas came back from South Africa with twin monoblocs that certainly looked original. It also had the 6 start oil pump, but someone had definitely been in side the engine. The factory records show extras as a large petrol tank, no mention of carbs.

Bernhard · Jan 6, 2020

Norton if you go by their own factory records and green workshop manuals did not fit the 6 start worms until mid 1966, and they also changed the oil pipe block to the pump which had larger holes from that to the pump in the crankcase, different rocker spindles with flats on, it's all in their 66 green w/shop manual.

One more Atlas question ....Carbs

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