Oil pump and rocker spindles

pommie john · Mar 13, 2014

My question is about the correct rocker spindles to use with my Atlas/Commando 750 hybrid.

It has a 3 start oil pump, but it has the pressure rocker feed coming from the timing cover just below the pressure relief valve.

Can I use plain rocker spindles with this set up ?

I know they should be scrolled if the supply is from the return oil line, and they should be plain if the 6 start pump is fitted, but what is best if it has the pressure feed from a 3 start pump?

toppy · Mar 13, 2014

I believe you can just change the pump drive gear and crank gear to a six start type and that should give you the standard pressure rocker feed set up to use with your plain spindles.

pommie john · Mar 13, 2014

toppy said:
I believe you can just change the pump drive gear and crank gear to a six start type and that should give you the standard pressure rocker feed set up to use with your plain spindles.

Yeah, that's a definite possibility. I'm wondering if I can get away with the plain spindles with the 3 start. It's not like the rockers need a massive oil flow. Dunno though.

I have heard that if you suspect over-oiling to the head you can run the bike for 10 miles with the rocker feed disconnected. That implies that oil supply to the head is not critical.

dynodave · Mar 13, 2014

For a pressure rocker I would always use a unscrolled shaft whether 3 or 6 start.
and for return or puke pressure I'd use a scrolled shaft.

pete.v · Mar 13, 2014

I must ask, what is the difference from a 3 start and a 6 start pump. Pictures?
Please don't say 3 starts.

L.A.B. · Mar 13, 2014

pete.v · Mar 13, 2014

I knew that. Thanks LAB, I thought it might be some internal that i was not aware of.

pommie john · Mar 13, 2014

dynodave said:
For a pressure rocker I would always use a unscrolled shaft whether 3 or 6 start.
and for return or puke pressure I'd use a scrolled shaft.

Thanks. I'll run it with the plain spindles then.

Is there any reason I should or shouldn't fit a 6 start gear set on my pump?

pete.v · Mar 13, 2014

So a 6 start crank worm will gather 6 pump gear teeth per rev with 14 teeth. = 2.33:1 2.33 worm turns to one pump rotation.

Known is the number of turns on a three, gathering 3 per rev, start but how many teeth on a pump gear to match the 3 start? If the pump on this set is also 14 teeth the 4.66:1.

It seems the variable term is "Hybrid". Is this an Atlas head?. What axactly what is determining a hybrid.

I would think that is running a Commando case then a 6 start set may be proper and the relative part will be the spindle.

dynodave · Mar 13, 2014

pommie john said:
dynodave said:

For a pressure rocker I would always use a unscrolled shaft whether 3 or 6 start.
and for return or puke pressure I'd use a scrolled shaft.

Click to expand...

Thanks. I'll run it with the plain spindles then.

Is there any reason I should or shouldn't fit a 6 start gear set on my pump?

If I had the gear set for 6 then I would probably run it.

PeteV:
same number of teeth but the the angle of the teeth is twice as steep for 6 start

toppy · Mar 14, 2014

pete.v said:
I knew that. Thanks LAB, I thought it might be some internal that i was not aware of.

The pumps are the same it is just the outer drive gears that where changed.
Somewhere on this forum is a thread showing pictures of commando an dominator pumps if you look it shows domies have small flat on body that later pumps didn't have but that's all

pommie john · Mar 14, 2014

pete.v said:
It seems the variable term is "Hybrid". Is this an Atlas head?. What axactly what is determining a hybrid.

I would think that is running a Commando case then a 6 start set may be proper and the relative part will be the spindle.

The bike was built from several boxes of bits 30 years ago. The engine number says it is a 1964 Atlas, but the timing cover os 750 Commando and that feeds the rockers. the head has oil banjos on the top so it must be Atlas, when I took the spindles out two were scrolled with a flat ground in them, and two were scrolled but had no flat.

You see my problem?

I intend to run it with the 3 start oil pump and plain rocker spindles to start with, and maybe fit a 6 start later and see how it goes.

Thanks for the help everyone.

pete.v · Mar 14, 2014

Yes, it's always wise to keep your options open with these darn things. I might think a pressure guage would be handy, at least till you sort it(and maybe beyond).

Bernhard · Mar 14, 2014

Norton went to 6 start oil pump drive back on the Atlas in 1966.
I converted my 1965 Atlas to this with a Commando rocker oil feed with no problems other than I did not clean out the pressure relief valve out which eventually blew off the Commando pipe at the joints.
The pressure relief valve (that big domed nut on the timing cover) was clogged up with muck and was overdue for a clean.
You live and learn.

Oil pump and rocker spindles

pommie john

toppy

pommie john

dynodave

pete.v

L.A.B.

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pete.v

pommie john

pete.v

dynodave

toppy

pommie john

pete.v

Bernhard

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