Difference between 3 start and 6 start oil pump?

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Oct 18, 2018
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Hey,
Every time I put on six start in replace of 3 start I moved overhead rocker feed to bottom of the timing chest ala commando style, scrolled or not, I have ruined more cams by lack oil flow from head then any soft cam problems ever encountered.
Never ran down Atlas cam tho!
One trick was open oil tank on Atlas and put you finger on oil return momentarily to flush oil to head, now who showed me that trick :)
nortonmark
 

Gilesy

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FWIW .... My '63 Atlas, actually a '62 build date, came from the dealership fitted with a 6 start oil pump. As I am the original owner, I can attest to that fact, curious as it is. The rest of the rocker gear is the scrolled type, typical of the 3 start systems. I have no idea whether the bike was a special Norton build, or a Berliner modification. From what I know of the dealer, he most likely DID NOT make the modification.

In 85K miles, I have not had any problems with this combination (6 start pump + scrolled rocker spindles). Thus, I would say, based on this experience, adding a 6 start pump + drive gear to older engines with scrolled rocker spindles should pose no problems.

Slick

PS: the easiest way to distinguish 3 vs 6 start worm gears, is to look at the worm gear face straight on (as if viewing an analog clock). The "starts" are where the gear lands begin their cut. As you view around the circumference, there will be 3 or 6 starting cuts.
Yes, my 1962 Atlas has a 6 start pump and scrolled spindles, but as to whether it was supplied like that, I don't know. I have had no issues with over oiling.
 
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There appears to be some dispute as to when the 6 start worm oil pump was supplied by Norton.

I suspect that, as it was officially fitted from 1966 on, according to the green Norton workshop manual, British suppliers like Dunstall etc, supplied them in their catalogue, and I suspect that Doug Helne fitted them on their overhead rocker supply 500 Domiracer from 1961. Feel free to correct me if I’m wrong.
 
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There appears to be some dispute as to when the 6 start worm oil pump was supplied by Norton.

I suspect that, as it was officially fitted from 1966 on, according to the green Norton workshop manual, British suppliers like Dunstall etc, supplied them in their catalogue, and I suspect that Doug Helne fitted them on their overhead rocker supply 500 Domiracer from 1961. Feel free to correct me if I’m wrong.

As seen in the NOC tech digest:
"From engine No. 116372 the con rods had a strategically placed hole drilled in order to squirt oil under pressure onto the cylinder bores. At the same time all models were fitted with a six-start worm drive on the oil pump, supposedly giving double delivery. Along with enlarged oilways, the rockers were now pressure fed from the delivery side of the pump. "

Engine no. 116372 was built at AMC in February 1966.
Enlarged oilways is underpinned by all NHT receiving new junction block and oil pipes.

1971-1976 oil pipes were 3/8" OD (5/16" ID) and no stepped sleeves were fitted on Commando models. Hose size was 3/8" ID and ferrules were fitted.
1966-1970 oil pipes were 3/8" OD (5/16" ID) having a stepped sleeves of 1/2" OD on all models. Hose size was 1/2" ID and ferrules were fitted.
1964-1965 oil pipes were 5/16" OD (1/4" ID) and stepped sleeves of 1/2" OD were fitted on G15 models. Hose size was 1/2" ID and ferrules were fitted.
1949-1965 oil pipes were 5/16" OD (1/4" ID) and no stepped sleeves were fitted on Dominator models. Hose size on Dominator models was 5/16 ID x 5/8" OD and ferrules were fitted.

-Knut
 
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