NHT Skimline low pressure rocker system

A friend has an early atlas with low pressure rocker oiler. Having added a commando style oil filter, he thinks the puke pressure line, originating at the tank fitting no longer feeds to the rocker line. (he pulled it off to check for flow)
Any one done this configuration with filter and found the oil not feeding and dripping out of the rubber jumper hose when opened/pulled off the head feed line.
Maybe it is slow because the air/oil puke is disturbed by running through the filter media. I can not conceive that it eventually would not collect enough oil to make it through the filter. However the oil tanks DOES receive oil based on the bubbles on the oil in the tank.
I'm thinking that maybe there is not enough head pressure to go up to the head but there IS enough to go in the tanks return line...
Should the T to the head connect before the filter??? which would provide some restricting pressure and force oil to the head also.

Hi Dave
I have hosed up the 650SS the same way, return line to the filter and then to the tank as per original, and all seems ok, I left the two unions loose on the head and plenty of oil came out.
After running I rechecked the valve clearances and noticed there was plenty of oil around the valves.

There is still the same amount of oil returning to the tank and the air has to go somewhere so it has to end up in the tank as well, so all in all it should still be the same.

I have noticed that the oil return is hard to spot in the tank, and when I check now I use a torch, and all seems fine.

Regards
Burgs

I have run several thousand miles with this set up on both an Atlas and a 650SS. I have a chronic slightly noisy tappet on the 650SS but this probably unrelated to oil delivery. Neither bike seems to have any problems. Scavenge side oil return is fine. Seems to me that if the system creates enough pressure to return oil through the filter there should be enough pressure for oil to bleed off into the rockers.

Burgs said:

Hi Dave
I have hosed up the 650SS the same way, return line to the filter and then to the tank as per original, and all seems ok, I left the two unions loose on the head and plenty of oil came out.
After running I rechecked the valve clearances and noticed there was plenty of oil around the valves.

There is still the same amount of oil returning to the tank and the air has to go somewhere so it has to end up in the tank as well, so all in all it should still be the same.

I have noticed that the oil return is hard to spot in the tank, and when I check now I use a torch, and all seems fine.

Regards
Burgs

Click to expand...

Thanks
The oil return I believe to be pointing inward in the tank away from the fill hole, so yes hard to see the flow. It may have been rumored, without confirmation, that the return tube end has a smaller hole in low pressure bikes than the .117" id return tube to cause back pressure and help the rocker oiling. We had discussed a possible custom brass plug/jet in the end of the banjo bolt to increase back pressure a bit...If the late slimline tanks have a BIG return hole then what causes the puke back pressure needed to divert the flow?

Bodger said:

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Seems to me that if the system creates enough pressure to return oil through the filter there should be enough pressure for oil to bleed off into the rockers.

Click to expand...

Making enough pressure to go through the filter seems is mostly assured. The pressure going up to the tank return, after the filter, which seems lower than the head tubing and the fear is the oil goes in the tank just fine but there is not enough residual pressure for the final climb to the head.

anyone dismanteled slimline tanks? I wonder if with a dental mirror I could inspect the back side holes of the return tube in a few tanks I have on the shelf...small for puke pressure and larger for high pressure returns?

I'll report back if I find any measurable differences...

dynodave said:

Any one done this configuration with filter and found the oil not feeding and dripping out of the rubber jumper hose when opened/pulled off the head feed line.

Click to expand...

Dave
I was worried about this for my ES2 so elected for a lower back-pressure oil filter - ended up using an Oberg P400 (https://www.obergfilters.com)
I teed off the rocker feed after the filter and have verified good flow to the rockers.
I mounted it on/behind the engine plated just below the front of the swingarm (almost same frame as your friend's).
Maybe a consideration?
Cheers
Rob

In theory, the pressure at the inlet to the oil tank (at the bottom where the banjo to the rocker box is fitted), is exactly the same whether an oil filter is upstream of this point or not.

With an oil filter fitted, the pressure at the oil junction block is increased by the pressure required to push oil thru the filter. Thus if one where to tee off rocker feed at the oil junction block (or at the filter inlet), the oil flow to the rocker box will be increased, possibly by too much, especially if the filter is dirty.

I have an inline oil filter on my Atlas. The take off to the rocker box is factory stock. I considered a tee tap up stream of the filter, but ruled it out because it might cause over oiling.

Slick

Oil delivery with the std low pressure system does seem a bit hit/miss ,some bikes get enough, some like my 99 got very little and wore out the valve gear. I think the pattern of use also has a bearing.Lots of short runs or low revs may not work. Also thick cold oil may not help. Some detergent content may help keep the small oilways clear. I have modified my oilways and it took a while to get the flow satisfactory. Too much is as bad as too little.

What is considered an acceptable pressure/volume of oil to the rockers, and when do you start considering a feed-side system?

How is everybody measuring anyway? Is anyone measuring a pressure head above the spindles with a length of clear tubing, or only an actual volume of oil pooling in the head?

Seems these days a return-side oil filter is a good idea.

Traditionally valve gear got by with minimal oil supply with iron guides, and wear was an accepted result of clean combustion with no oil seals. Some oil was considered "enough".As soon as a proper flow is introduced oil gets burnt and valve seats can suffer. The forward leaning Commando motor at least got better drainage.Fitting oil seals to Dommy Inlets allows a bit more flow. If you want to really improve the flow an external oil drain at the back of a Dommy motor would be a good mod.