How Much In A Tea Cup?

(oh my god not another wet sump thread!?)
It's often said that a Commando will always have a teacup of oil in the sump, with that being said;
I just drained the sump of my MKIII and drained 28 oz. (940 ml) of 20/50 Valvoline.
This is after 'Pa' my trusty Norton sat for 8 days.
This is after AMR did the magic trick to the oil pump and timing cover.

The question is; of that 28 oz. how much extra is from wet sumping?

How low can the oil level in the tank go before I blow out the main seal (again) when starting with a sump full of oil?
Whats my next step to stop this dreaded condition, its driving more anal than usual?

And another thing; does anybody else think that the spring holding the 'check' ball against the seal is a little on the weak side? There is that big tank of oil being held back with a spring that wouldn't be strong enough to operate my cheap ball point pen,,,,,,,,,,,,,,,,,oh god somebody stop me!!!!!!!
Ride On (regardless)
Dave

Well, I just happened to be making my morning cup of tea so measured it - 7.5 fl oz (i'm sure it is an ISO standard cup too - NOT!)
So you're getting good value - four cups for the price of one!
Cheers
Rob

Why not do a little experiment. When you come in from a ride, pull the drain plug and see how much oil drains. Then pull it again after 7 or 8 days and compare.

Personally, I don't worry about wet sumping. I check the tank if it has been sitting a week or so. If the screen is covered I start it and and watch for the oil to return to near normal. If the screen is visible, I'll drain the sump and add back to the tank, although you can also kick it over a few times and the scavenge side of the pump will return enough oil to cover the screen.

And I've never blown out a crank seal.

The check valve in my Mark III apparently doesn't do a damn thing. It wet sumps just as much as my Mark II
But I don't worry about it because I installed a Jim Comstock sump reed valve which very quickly forces all
of that oil right back to the oil tank rather than letting pressure build up in the sump to blow out the oil seals
while waiting for the oil pump to scavenge the sump.
If the oil pump didn't leak down the oil tank, I would expect 6-8 ozs of oil in the sump at the end of a run.

In my reply to a similar thread I mentioned that my 850 would drain the oil to below the tank's output fitting in 7-10 days when I bought the bike in 05. I resurfaced the oil pump per the Norton service manual and since then, it can go 2+ months with the oil still above the tank outlet fitting. IMO, that pretty much eliminates the "problem." If it has to sit longer than that, starting/running the bike for a couple of minutes every couple of months doesn't seem to be that big of a deal.

The Buckeye Rider said:

(oh my god not another wet sump thread!?)
It's often said that a Commando will always have a teacup of oil in the sump, with that being said;
I just drained the sump of my MKIII and drained 28 oz. (940 ml) of 20/50 Valvoline.
This is after 'Pa' my trusty Norton sat for 8 days.
This is after AMR did the magic trick to the oil pump and timing cover.

The question is; of that 28 oz. how much extra is from wet sumping?

How low can the oil level in the tank go before I blow out the main seal (again) when starting with a sump full of oil?
Whats my next step to stop this dreaded condition, its driving more anal than usual?

And another thing; does anybody else think that the spring holding the 'check' ball against the seal is a little on the weak side? There is that big tank of oil being held back with a spring that wouldn't be strong enough to operate my cheap ball point pen,,,,,,,,,,,,,,,,,oh god somebody stop me!!!!!!!
Ride On (regardless)
Dave

Click to expand...

The link below is from an older post but gave an excellent systematic approach to identifying the source of rapid wet sumping.

https://www.accessnorton.com/Norton...elief-valve-and-amr-modification.18868/page-2

To save you the time of hunting through the linked topic I have provided the italicized text below.

If you are not happy with the rate your motorcycle is wet sumping it is possible to isolate where the leaks are happening. First you can remove the rocker feed line and just observe how much oil comes out of the oil passageway. If the oil just keeps running out after a period of time then it is safe to assume that your anti wet sump valve is not seating properly. Of course if the oil stops draining there then the anti wet sumping valve is ok. With the Mark III timing cover the oil pressure relief valve has nothing to do with wet sumping.

Unfortunately the 1972 Norton does not have a sump screen which would have been handy by removing and visually checking whether the oil is back flowing through the scavange pump pickup.

Now you can remove the timing cover, plug the oil pump outlet, plug the threaded hole in the engine case and disconnect the oil return hose that goes to the oil filter. Clean the pump and the area all around really well. Over a period of time visually inspect to see where the oil is leaking externally. If it is leaking at the brass end plate seam, resurfacing the plate and the pump body should really help. If it continually leaks out through the oil pump's input shaft that would indicate there is an internal leakage of the pump from the delivery side to the scavange side. This is what the AMR o-ring modification corrects. Also if there is a leak around the area where the oil pump is mounted on the engine case it could mean that the gasket is shot or the mounting nuts/studs are loose. When I took my bike apart the mounting nuts were barely snug and the studs were loose in the engine case.

These are ways of methodically isolating the cause of rapid wet sumping on your engine. I hope this is of some help.

Peter Joe

Thanks Kurt. That is really the information I was looking for. I'm on it till it's fixed.
Ride On
Dave

The answer to my tea cup question; How Much In A Tea Cup?;
I rode 'Pa', my trusty Norton to our monthly British Bike Club meeting and when we returned home I let it sit for twenty minutes then drained the sump and filled the catch can with 10 oz. of hot 20/50.
I will get to the bottom of this. (pun intended)
Ride On
Dave