Sump, 'Correct' Volume of Oil

Mart UK said:

I opened the drain plug about 3 hrs after a ride and collected over twice that volume (c.15fl.oz, 400ml). How 'generally'?

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There would also have been a certain amount of oil in the timing case that (unless the low hole modification has been done, see link, below) would have drained to the sump through the timing side bearing fairly quickly after the engine had stopped and probably accounts for the greater quantity than when left to drip.

lazyeye6 said:

What comes first, the chicken or the egg? Is there such a thing as a "standard" or usual amount of oil to wet sump,
and over what period or time? ok, 2 variables. Answer: Every bike is different. Want to find out? drain the sump
and wait a measured amount of time. Then drain the sump again. That is the answer. Then, either ride more often,
or install that nifty Feked manual valve with the ignition interlink. Or don't. Maybe do both and stop worrying.

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That's what I have on my 850, fitted it years ago, never been any problem.

L.A.B. said:

There would also have been a certain amount of oil in the timing case that (unless the low hole modification has been done, see link, below) would have drained to the sump through the timing side bearing fairly quickly after the engine had stopped and probably accounts for the greater quantity than when left to drip.

Pre Combat timing case mod (2015)

My 1970 Fastback that seized with the wet sumping valve issue is about to go back together. All the drilling mods to the timing cover tend to deal with the Combat engine and later. Many years ago (30+) I followed the top tips in the NOC technical handbook and did away with my camshaft breather...

www.accessnorton.com

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Thanks. Have I understood this?
- The location of the drain hole(s) sets the oil level in the timing case, whilst the engine is operating?
- While operating, the oil passes through the drain hole to the sump, to be scavenged back to the oil tank (via external filter)?
- Once turned off, the oil above the timing side bearing (the lower of the two?) Slowly drains down through that bearing to the sump?

For my bike, there's no record of any change to the timing case, so that would suggest a fair volume of hot oil would drain down through that bearing.

When people experience burning sumped oil, blowing the crank to primary seal, or hydraulic locking, how much oil are we talking about in the sump? Presumably, more than that volume, plus what typically sits below the pump, in the sump (in my case about 400ml/15fl.oz)?

I've been exploring this area because I occasionally get a smokey LH exhaust on start up (after being on centre, not sidestand). But only occasionally. I partially suspect guide valve oil seal, but don't understand why it is only occasionally, so wanted to rule out sumping. I also knew I should be rid of the automatic anti-sumping valve, not just in case of failure, but also to avoid it reducing flow from the tank to the oil pump.

Mart UK said:

Have I understood this?
- The location of the drain hole(s) sets the oil level in the timing case, whilst the engine is operating?
- While operating, the oil passes through the drain hole to the sump, to be scavenged back to the oil tank (via external filter)?
- Once turned off, the oil above the timing side bearing (the lower of the two?) Slowly drains down through that bearing to the sump?

For my bike, there's no record of any change to the timing case, so that would suggest a fair volume of hot oil would drain down through that bearing.

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Yes, I believe so.

Mart UK said:

hydraulic locking

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As I understand it, it cannot hydraulically lock because the oil in the crankcase even when fully 'wetsumped' wouldn't rise to a high enough level for the piston skirts to 'dip' into the oil at BDC, also the crankcase isn't a sealed chamber so unless the crankcase became drastically overfilled then there would always be airspace between the piston skirts and the oil.

L.A.B. said:

Yes, I believe so.



As I understand it, it cannot hydraulically lock because the oil in the crankcase even when fully 'wetsumped' wouldn't rise to a high enough level for the piston skirts to 'dip' into the oil at BDC, also the crankcase isn't a sealed chamber so unless the crankcase became drastically overfilled then there would always be airspace between the piston skirts and the oil.

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Yes but...
A substantial amount of oil (incompressible) in the crankcase would substantially raise the pressure there as the pistons come down. That could, depending on that pressure, lead to the drive-side seal blowing out.
So.. not a hydraulic lock (otherwise the engine would not turn) but something close, and enough to do damage.

robs ss said:

Yes but...
A substantial amount of oil (incompressible) in the crankcase would substantially raise the pressure there as the pistons come down. That could, depending on that pressure, lead to the drive-side seal blowing out.

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Yes, it will increase air/gas pressure in the crankcase that can result in a blown seal but not from a hydraulic lock.

robs ss said:

Yes but...
A substantial amount of oil (incompressible) in the crankcase would substantially raise the pressure there as the pistons come down. That could, depending on that pressure, lead to the drive-side seal blowing out.
So.. not a hydraulic lock (otherwise the engine would not turn) but something close, and enough to do damage.

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Is that the seal on the shaft that goes through to drive the primary sprocket?

At the moment:
- 100ml now in measuring jug, since Sunday evening
- So, about 35ml a day, only one to two drops a minute. Not enough to warrant work in the engine, nor an obstruction (shut off valve) in the oil feed line, in my amateur opinion.

Given 400ml is the start point, due to the timing chest draining, how many days @35ml/day, before I should empty the sump prior to starting? E.g. 10 days = 750ml in the sump. Too much?

If I empty the sump, does that mean it will then take longer to get the oil fully circulating from the tank, or is the pump still fully primed to get oil to where it's required?

I'm not overly worried, so far I've been riding every few days, but over the coming months that will change along with the weather! May as well avoid a potential problem.

Mart UK said:

Is that the seal on the shaft that goes through to drive the primary sprocket?

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Yes, but the Mk3 also has a circlip to prevent the seal from blowing out.

Mart UK said:

Given 400ml is the start point, due to the timing chest draining, how many days @35ml/day, before I should empty the sump prior to starting? E.g. 10 days = 750ml in the sump. Too much?

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You could leave it until it's just beginning to show the oil tank gauze. The greater the quantity in the sump the harder it gets to kickstart if the electric starter isn't used.

Mart UK said:

If I empty the sump, does that take longer to get the oil fully circulating from the tank, or is the pump still fully primed to get oil to where it's required?

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Assuming you put that oil back in the tank then the draining will continue even if the tank has emptied (as far as it possibly can) so there's no need to prime the pump.

What I suggest you do if you know the bike isn't going to be used over the winter etc. is drain/pump/syphon the oil from the tank into a container before it can drain to the sump, just remember to put it back before starting the engine.

How does enough pressure to blow a seal build up in a crankcase if there is a crankcase vent?

MexicoMike said:

How does enough pressure to blow a seal build up in a crankcase if there is a crankcase vent?

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Depends on which type of crankcase breather the engine has (timed, 200000 '750', or 850) I'd guess.

L.A.B. said:

Yes, but the Mk3 also has a circlip to prevent the seal from blowing out.



You could leave it until it's just beginning to show the oil tank gauze. The greater the quantity in the sump the harder it gets to kickstart if the electric starter isn't used.



Assuming you put that oil back in the tank then the draining will continue even if the tank has emptied (as far as it possibly can) so there's no need to prime the pump.

What I suggest you do if you know the bike isn't going to be used over the winter etc. is drain/pump/syphon the oil from the tank into a container before it can drain to the sump, just remember to put it back before starting the engine.

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I plan to use the bike over the winter, when the weather looks inviting, so not as often. The gauze check is useful. Thanks.

So, if I've left it a while, provided some oil remained above the pump, all I need do is empty the sump into the tank and good to go?

Mart UK said:

So, if I've left it a while, provided some oil remained above the pump, all I need do is empty the sump into the tank and good to go?

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As long as the feed gauze is partially submerged then you should be safe to start the engine as once the engine has started then the scavenge should soon begin to refill the oil tank. A sump full or fairly full, makes starting more difficult as mentioned, and each time the drain plug is removed and replaced it's wearing the crankcase threads so should be reduced to a minimum wherever possible in my opinion or buy the large sump plug with the drain bolt.

https://andover-norton.co.uk/en/shop-details/16995/magnetic-crankcase-sump-filter-kit

Good suggestion. I've got one on order, along with some spare oil filters. Thanks for your help.

The drilled port (oil gallery) from the large sump plug to the oil pump scavenge port, is above the sump bottom. Therefore, some residual oil is always in the sump after engine shutdown. How much oil? As stated above, about a cupful.

If you wish to know exactly, run the engine a few minutes, shutdown, remove the large sump plug, and measure.

Slick

200ml, which after 3 to 4 hours became 400ml. At this point it increased at 30 to 35ml per day, or a drip every 2m25s. The swift increase shortly after shutdown was @L.A.B.'s suggestion of draining through the bearing into the timing chest. The 35ml/day is my rate of wet sumping. Not that I'm anal about it...

Mart UK said:

The swift increase shortly after shutdown was @L.A.B.'s suggestion of draining through the bearing into the timing chest.

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Out of, not into the timing chest.

My dipstick is not vertical (not 90 degrees to the plane of the oil cap). It has a slight angle. So I get a higher or lower reading with a difference of about 1/3 between H and L marks, depending on which direction of lean. Not a problem, now I've realised, but should it be vertically straight down? Looks like it in the AN parts photo.

I know I keep raising some inane queries. Getting to know the design and dealing with how it's been modified / "improved" or neglected over 46 years since it left Andover.

L.A.B. said:

Out of, not into the timing chest.

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Yes, of course.

Mart UK said:

My dipstick is not vertical (not 90 degrees to the plane of the oil cap). It has a slight angle. So I get a higher or lower reading with a difference of about 1/3 between H and L marks, depending on which direction of lean.

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The oil would normally be checked with the bike vertical.

Mart UK said:

Not a problem, now I've realised, but should it be vertically straight down? Looks like it in the AN parts photo.

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But, the filler neck isn't vertical.

L.A.B. said:

The oil would normally be checked with the bike vertical.




But, the filler neck isn't vertical.

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Yes, always check on centre stand. I may not be explaining myself very well. With my oil cap, it's possible to put it into the gaps in the lip of the filler in two different orientations, 180 degrees apart (orientation A and orientation B). I didn't think it mattered that the filler neck isn't vertical, so long as the dipstick always enters the oil at the same point regardless of which way round I'd inserted the cap, I.e. A and B always enter the surface of the oil at the same point.

At the moment, if you look side on at my dipstick, it leans, I.e. if you stand the cap upside down on the bench, the dipstick isn't straight up, it leans, the fold is greater than 90 degrees. My dipstick definitely doesn't read the same if inserted into the tank using orientation A vs B. I think, because it goes into the oil at different angles, because the filler neck is angled, giving different readings, depending on which 180degree orientation of the cap. It's like if you dip a screwdriver into the tank, down into the oil in line with the filler neck you'd get one reading, off at an angle to the filler neck, you get a different reading. If you get my drift!