Difference between 3 start and 6 start oil pump?

baz

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Is there a visual difference between the 6 start and 3 start pump?
I have never seen the 3 start and I want to know how to identify one?
Many thanks
 
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Its the worm gear that determines the number of starts, part of the definition of a worm gear is the number of starts. There may have been an increase in thickness of the feed gears but not certain.
 

baz

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Its the worm gear that determines the number of starts, part of the definition of a worm gear is the number of starts. There may have been an increase in thickness of the feed gears but not certain.
Ok thanks for that, that's something I didn't know
So does the drive on the pump remain the same amount of teeth
And only the worm drive on the crank differ?
Cheers
 
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Us in america have incredibly few early machines to study off of. Also incredibly few in north america actually care about precommando. Some do...
Drive gear sets 3 or 6
This is independent of the pump version.
The crank gear/nut has 3 or 6 lobes looking onto the end profile.
The pump gear and crank gear must match. They will mesh together at 90 degrees when matched.

Norton Heavy Twin pumps all generally visually the same.
Early pumps have the thin feed .190" and thin scavenge .310" gear set. My 52 M7 oil pump was nonferrous zinc or aluminum body. Not sure on change over year to iron body.
Later current wide gear pumps are .250" feed and .397" scavenge gear sets.
Fettling of the feed gear side pump body is over hyped as a "rebuild".
At best it is a low level refurbishment that improves only 1 of 4 wearing aspects of the pump.

4 body screws 2BA
shaft nut early 3/8 26CEI, late 3/8 24 unf
 
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Bodger

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Question to Dave, what is your opinion of using a new pump with existing 3 star crank gear and pump gear? Would this work and negate the possibility of rocker over oiling issues. Curious - I have two early three start bikes.
 
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Question to Dave, what is your opinion of using a new pump with existing 3 star crank gear and pump gear? Would this work and negate the possibility of rocker over oiling issues. Curious - I have two early three start bikes.

AFAIK New pumps are now only made in wide gear sets.
Wide gear set pumps started in 195?...what years (wide/narrow gears) are your bikes?
3 "start" pumps are normally matched with the scrolled rocker style and 6 "start" go with 66+ solid rockers.
With no other option for narrow pumps I would use a new wide gear pump and use the appropriate gear set.
I highly doubt I would use a 6 start on a scrolled rocker engine.
 

texasSlick

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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.
 
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Bodger

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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.
That's really interesting. Conventional wisdom would have it that that combination would cause over oiling of the scrolled rockers, but if your set up has the return fed - not pressure fed - oil supply to the rockers it would make sense that the extra flow/pressure(? ) would not have any effect on the rockers. Of course I cant remember how many starts the gears on my '62 Atlas and '64 650SS have. I've just always assumed they were 3 start and of course I didn't take any photos the last time I had the timing covers off.
 

texasSlick

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@Bodger #11

My Atlas has the low pressure return rocker feed. Others have reported over oiling problems if the rocker feed is modified to the high pressure type, without changing the spindles to the high pressure type. IMO, such over oiling (high pressure feed + low pressure spindles) will occur with either 3 or 6 start pumps.

Slick
 
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s-l1600.jpg
 
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assuming the pix are correct, the outer shape of the pumps around the bottom mounting holes are distinctly different, the 3 start is notched (clearance bevel on one end of the pump body) vs rounded on the 6 start

then again, this one on ebay advertised as year 70 is notched
"1970 NORTON COMMANDO COMPLETE OIL PUMP ORIGINAL OEM 06-3037"
https://www.ebay.com/itm/1970-NORTO...h=item3d4f97b4b7:g:6F4AAOSwzppaDgBD:rk:8:pf:0

this notched one advertises fitting
"NORTON-OIL-PUMP-ATLAS-77-88-99-COMMANDO-750-850-COMBAT-FASTBACK-ROADSTER-N15-"
https://www.ebay.com/itm/NORTON-OIL...=item33f88c8953:g:-NMAAOSwIbtb2yR7:rk:47:pf:0


stumbled this
http://centralcoastclassicmc.com/NortonOilPumps.htm

new one here shows no bevel
https://www.classicbritishspares.com/products/norton-commando-oil-pump-06-6193
ad sez
Replaces Norton part number 06-6193, 066193, 06-3037, 063037 and NM25368.
Oil pump comes complete as shown (excluding the worm gear). Fits all Norton commando models both 750 and 850 from 1969 to 1975. Also fits other Norton models such as the Dominator, etc. Check your parts book to ensure the best fitment.

https://www.accessnorton.com/NortonCommando/p11-p11a-750-ranger-engine-thread.18418/#post-274466
 
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the differences are into shape/size of inlet/outlet for the oil holes , 3 start = 2 round + 1 oval/elliptic..., 6 start= 1round + 2 oval/elliptic...
the bevel had been present on both 3 and 6......
 
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That's really interesting. Conventional wisdom would have it that that combination would cause over oiling of the scrolled rockers, but if your set up has the return fed - not pressure fed - oil supply to the rockers it would make sense that the extra flow/pressure(? ) would not have any effect on the rockers. Of course I cant remember how many starts the gears on my '62 Atlas and '64 650SS have. I've just always assumed they were 3 start and of course I didn't take any photos the last time I had the timing covers off.

Unless someone brought and fitted a 6 start worm gear and drive they were 3 start, Norton did not change to 6 start at, I believe, the middle of 1966. You then have the bigger oil block feed/return pipe, bigger oil holes drilled in the crankcase and possibly someone has fitter a Commando rocker feed pipe, making the old type rocker feed from the return pipe redundant.
 
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1. Norton Heavy Twin pumps are all "generally" visually the same.
Some do have the bevel.... is it not for clearance when used on singles?...not needed for NHT

2. As TS indicates, and I agree, the rocker feed type is more associated as low pressure = scrolled rocker shafts and high pressure = plain rocker shaft and 3 or 6 start is less important.

When I get a chance I will test whether the feed oil outlet port size actually makes any difference in flow, I doubt the junction block and tube/hose differences affect final flow. The "S" tank and fastback tank had huge lines and the 850 were much smaller.
 
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