Five minute wet sump?

Today I went for a ride about 20 miles, parked the bike and about five to ten minutes later checked the oil and it wasn't even showing on the dipstick, started the bike and seconds later it was up to just below the top level. I had had the bike standing for about six weeks and the oil level had dropped till it was just touching the bottom of the dipstick. Does this mean it 'wet sumps' in a matter of minutes to a low level then remains at this low level or whats happening?

That sounds disturbingly quick to pump it all back up into the tank ??

You need to take it for another ride tomorrow, and check more things.

How full is the oil tank tomorrow morning.
How long does the tank take to get back to full on the dipstick, after you start it.

If you pull over somewhere after a few miles, switch off and check the oil level in the tank on the dipstick.

Hm, life is full of mysteries but one would expect most the wet sump to occur with heated thin oil. Best habit is peek in oil tank on each shut down so if none seen in tank on next start up you have idea of how much to add to top off back to normal running level. I'm rather pleased how fast more than enough oil refills empty tank on start ups so if empties tank in under an hour parked and not checking oil tank before heading out again, no big deal, just don't make hobot habit of it. Leaving crank at TDC vs BDC may be a factor.

Oil can only leak past the oil pump into the cases.
Check the oil pressure immediately.
Ta.

When was the T.Cover off last to replace the tiny oil pump conical seal ? Heated rubber seals don't last forever .

edward,
I would be looking. :shock:
Time to remove the Timing cover. Best to replace the seals while your in there. Two in the cover and one on the pump.
New gasket as well.
Cheers,
Thomas
CNN

Wet-sumping got me in a heap of trouble just before I left N-V. After I'd given my notice that I was emigrating to the US, I took my wife up to her folks' place in Lancashire on the back seat of the 650SS "hack" I rode. I hadn't used it for a while, and when I checked the oil before we left, the tank was nearly empty, so I filled it.

When we got to her folks' place, about 120 miles away, she got off the back seat and found one of her shoes completely soaked with oil. I wasn't the most popular guy on the block! I realised later that the engine had "wet-sumped" and probably had a full tank of oil sitting inside the engine.

Unfortunately, I had a gasket failure at the oil line connection to the crankcase on the way back to Wolverhampton after the weekend, and the trusty 650SS seized up on the freeway. It went back to the plant in a van. I don't know what happened to the old girl as we were on an airplane to Seattle a few days later. In retrospect, I wish I'd been able to bring that bike to the US. Sure, it rattled your fillings a bit, but it was a very dependable performer. Maybe it was as well that I didn't, as I found the transition to driving on the opposite side of the street to be difficult, for the first couple of months. Driving a car, you had the additional cue of sitting on the other side. On a bike, you didn't.

needing said:

Oil can only leak past the oil pump into the cases.

Click to expand...

Oil could also drain from the OPRV return drilling at the timing cover joint, if say, the gasket surrounding the drilling was damaged, and also leak down through the OPRV (not 850 Mk3) especially if it had jammed in the open position.

Hi LAB.
With your scenario, oil is not just draining from the tank as the OPRV is beyond the oil pump (the pump is pressurising the 'sump').
I say again, check the oil pressure immediately.
Ta.

needing said:

With your scenario, oil is not just draining from the tank as the OPRV is beyond the oil pump (the pump is pressurising the 'sump').

Click to expand...

I'm not sure I understand what you are saying about the pump pressurising the sump-but with the engine stopped-oil can flow from the oil tank to the sump through the OPRV and crankshaft (except 850 Mk3). Oil doesn't necessarily have to pass through the pump to get to the sump.

Hi LAB.
Re your: "...Oil doesn't necessarily have to pass through the pump to get to the sump...."

You had better draw me a picture to explain your rationale for this assertion.
Ta.

Check your primary chain case oil level. I bet you will find oil passed by the crank seal & into there. I would be worried a seal has blown with it sumping that fast.

needing said:

Hi LAB.
Re your: "...Oil doesn't necessarily have to pass through the pump to get to the sump...."

You had better draw me a picture to explain your rationale for this assertion.

Click to expand...

On the pre Mk.3 Commandos, when the engine is running, oil blow-off from the OPRV recirculates back to the inlet side of the feed pump through the timing case-to-crankcase drilling, so there is a direct path between the OPRV and the feed from the oil tank.
Once the engine has stopped, oil can potentially flow in the opposite direction from the feed line to the OPRV if the valve was stuck open or leaking and then drain through the crankshaft to the sump.

It is also why it is often necessary to temporarily thread a timing cover screw into the crankcase drilling at the cover joint whenever the timing cover has been removed to prevent the contents of the oil tank from draining out through the drilling.

L.A.B. said:

It is also why it is often necessary to temporarily thread a timing cover screw into the crankcase drilling at the cover joint whenever the timing cover has been removed to prevent the contents of the oil tank from draining out through the drilling.

Click to expand...

Is that why that hole is threaded? To plug while the cover is off? I knew it, there was purpose to their thinking.

pete.v said:

Is that why that hole is threaded? To plug while the cover is off? I knew it, there was purpose to their thinking.

Click to expand...

Or they'd had large puddles of oil on the workshop floor before.....

L.A.B. said:

needing said:

Oil can only leak past the oil pump into the cases.

Click to expand...

Oil could also drain from the OPRV return drilling at the timing cover joint, if say, the gasket surrounding the drilling was damaged, and also leak down through the OPRV (not 850 Mk3) especially if it had jammed in the open position.

Click to expand...

Thanks LAB.
Your later explanation now makes sense of this comment for me. The original poster can quickly eliminate this by assessing the OPRV upon removal.
Ta.

I wanted to go for some short rides and make some accurate measurements of the fluctuating oil level but we have been having the worst storms for ten years here for the last few days. What I did do was check the oil level after the bike had been parked about 4 days and to my surprise it was still above the low level on the stick, so the rapid draining that I initially posted about is obviously an intermittent problem, maybe it is the OPRV sticking sometimes? I will go into the timing chest later this week when I get the chance, have ordered some seals etc. in preparation.

edward said:

I wanted to go for some short rides and make some accurate measurements of the fluctuating oil level but we have been having the worst storms for ten years here for the last few days. What I did do was check the oil level after the bike had been parked about 4 days and to my surprise it was still above the low level on the stick, so the rapid draining that I initially posted about is obviously an intermittent problem, maybe it is the OPRV sticking sometimes? I will go into the timing chest later this week when I get the chance, have ordered some seals etc. in preparation.

Click to expand...

edward,
What is “Your” history to your bike????
Is it new to you?
Did you have it from new?
If not... do you know the original owner?
These are some of the things that tell the tail, I will call them opportunities that l would look to go to and investigate ….that is if it were my bike.
You need to clarify this in order to approach the original problem that you posted.
Cheers,
Thomas
CNN

To CNN
The bike is a Dreer Norton (imported from USA) which I've owned about 2 years, it has always wet sumped since I've had it but the process usually takes many days or weeks. What prompted my posting was that the last time I rode it, I found that when checking the oil only a few minutes after stopping, the oil tank level no longer registered on the dipstick, after restarting it rapidly went back to the nearly full mark then when stopped and checked a few days later it had dropped but was still on the low mark. I'm not saying this hasn't happened before but I've certainly never noticed it. The bike does have an oil cooler but I don't know if this is relevant. I use a fully synthetic oil as recommended by Kenny Dreer. I have done about 4,000 miles, when I bought the bike it had been stored for ten years and had less than 2,000 since it was built. I replaced the drive side crankcase seal very early on as it had gone hard and was allowing oil into the primary case. I have not had the timing cover off since I've owned it but I believe the pump is standard Norton. Maybe when the bike is actually being ridden the oil goes somewhere else? The oil cooler? Then when its idling it allows the tank to fill up again?

edward,
Well maybe it was the OPRV as L.A.B. stated.
I have found some weird things when I rebuilt my 74 with an idle shaft missing from my oil pump and the gears just staying there in the encapsulated cut out. :shock: It is corrected now. This last winter....3-month storage.
I live north of the 49th; my oil tank was about half full when I squinted in for a look-see. I just kicked it over and watched the oil spurt back from the Comstock breather then when that cleared I watched the oil return burbling away. 50-wt oil
Cheers,
Thomas
CNN