dommie top end oil supply

I am working on a Dominator. The usual oil supply for the top end is a banjo bolt off the return line offering a low flow to the rockers. The previous owner has this supply crimped off and is running a commando rocker line which is designed for a six start oil pump. This bike should have a three start though I have not checked. Is there a problem using the commando set up? Oil pressure drop?

seattle##gs said:

Is there a problem using the commando set up? Oil pressure drop?

Click to expand...

Does it have the high pressure rocker spindles?

not sure what your question entails .....
My Atlas came factory equipped with a six start pump; otherwise is typical Atlas/Dominator rocker oil supply, which is low pressure oil sourced from the scavenge return line to the oil tank. No problems running the 6 start pump with this configuration.

Is your Dominator sourcing its oil supply from the high pressure port located under the OPRV? If so, there can be a problem depending on whether the PO positioned the spindle flats properly. From memory, the flats should be placed outwards. Check me on this.....memory fails me at my age.

Slick

texasSlick said:

Is your Dominator sourcing its oil supply from the high pressure port located under the OPRV? If so, there can be a problem depending on whether the PO positioned the spindle flats properly. From memory, the flats should be placed outwards.

Click to expand...

That's if the original scrolled low pressure rocker spindles have been replaced with high pressure spindles.

Yes it's getting the oil from the port below the OPRV. Do not know about the spindles in the head. If it is using the 3 - start it's already low pressure so I am concerned that the oil feed ala commando would really drop the pressure. I will investigate the pump (six or three start) . The spindles would have too be Commando? in either case? Or should I go back to the drip feed from the return pipe if the head has the Dommie spindles?
I hava 1966 Atlas that came stock with a six start.

For high pressure it should have non-scrolled (Commando) spindles with flats facing out.

I have this set up on my Model 99 but suspect over oiling, nothing like the stories you read about though. I’m going back to the low pressure set up with scrolled spindles flats facing inward but keeping the six start pump like Slick’s setup.

In the uk its generally accepted that mixing the high and low pressure setups can bring over oiling and unnecessary wear . I would consider fitting the later ( bigger int gear) pump and use the 3 start gear set , inlet valve oil seals and a oil bleed modified rod on the drive side only. I am assuming you still have a cam oil bath detail.

Thanks Bob.

I’m curious about the wear you mention in mixing pressure setups?

Pumps wear , and wear twice as fast with a 6 start gear set. Valve seats burn out when they are subject to excess oil. Big ends fail if fed with over airated oil. The engine designers (not AMC!) knew what they were doing . It took AMC another 10 years to make their "improvements " worth the trouble.

My 1962 650SS is running the earlier, (pre-AMC) / correct for year "low pressure" system of oil supply to the head. I.e. feed is from the oil return pipe, 3 start gear, scrolled rocker spindles with flats facing inward.

I had problems with insufficient oil feed to the head, which this forum was very helpful fixing. The solution for me was: 1. A new oil pump from Norvil. 2. reducing the diameter of the oil return pipe, after the union to the head, in order to force more oil to the head. Apparently this is a not an uncommon mod, (is actually mentioned in my Norton manual) and for me works really well! That said, I try to make a point of not letting the old girl idle until I have given her some revs and therefore a good squirt of oil to the head!

I think the moral of the story is that the earlier system works absolutely fine, "if" setup correctly.

Cheers,

James

James has pretty much the same settup as my 99. Except I have an orriginal refurbished pump.

NorLuck said:

What is the correct line to get for 88/99-dominators/650ss/mercury bikes (that still looks good braided metal, mine is thin ugly black tube)?

Click to expand...

Low pressure rocker feed (from the scavenge?) or high pressure (from serial 116372) off the timing cover?
88/99 Dominator would normally be low pressure.
650SS (And 750 Atlas) could be either.
650 Mercury would normally be high pressure.
With, or without the rigid pipe section?

NorLuck said:

I'm glad I read this topic... Sorry if it's a bit of a hijack but I was told by Andover that it didn't matter if I bought a commando rocker oil feed line or a dominator one. My idea honestly was to buy this from Venhill because it looked nice. Now I'm not quite sure if the pressure will be correct or not. Actually maybe I shouldn't have read this topic I'm kinda confused haha...

NORTON OIL LINE (CYLINDER HEAD)

ALL 750/850cc COMMANDO MODELS. Please note these lines are made in un-covered stainless steel braided hose. No PVC cover, but a black heat protection sleeve is fitted on the longer lower hose. The lines are therefore not available in different colours | Includes 2 single bolts, 1 double...

www.venhillusa.com

What is the correct line to get for 88/99-dominators/650ss/mercury bikes (that still looks good braided metal, mine is thin ugly black tube)?

@seattle##gs what are you going with in the end product wise?

Click to expand...

Looking at the venhill oil line in the URL you posted, it could only be for the later "high pressure" oil system that bolts onto the feed on the rear of the timing cover and head. Would not work for the "low pressure" system, as stock, because there is no bolt to the oil tank scavenge, just the ugly black rubber tube with jubilee clip or whatever.

I think what Andover means, is that it is correct for any Dominator bikes running the "high pressure" oil system or Commando which should all be "high pressure".

NorLuck said:

I kinda like this kit, apparently it'll be fine on a Mercury (banjo bolts thread size tho?): https://andover-norton.co.uk/en/shop-details/16569

Click to expand...

The banjo bolt thread should be 5/16"- 22 BSF.

For low pressure feed one of these are needed at the oil tank return feed. I have not seen one of these as shown, but the original has a step inside that centers the banjo and these do not.

This Dommie was delivered as a non-runner that needed oodles of work. The oil line was a commando one which I made up a new one that curls up at the rear of the battery box then goes foreword, trying to hide the oil line. The original banjo on the return oil tank fitting is still there and crimped off in two places. So I began to wonder if the PO just slapped on a Commando oil line without considering the three or six start oil pump and the difference in output. It seems to me that if the Commando line is used with a three start low pressure pump then the oil pressure to the rods would drop off, especially with the stock scrolled spindles. I do not think switching to Commando spindles would help much to increase oil pressure. The original rocker feed was a very low, almost drip feed off the return line, like Triumphs.
I will investigate soon by removing the oil pump and removing a rocker spindle.
Notice the use of the word " I think". Do not know for sure, just some suspicions. I do not want to find out the hard way.
In a three start system how much oil pressure should there be? Of course, it only feeds the crank.

NorLuck said:

If so would mine be a six as I can count six points looking at it face on?

Click to expand...

Yes, and it has the (later plastic tube) high-pressure rocker feed off the timing cover.