Wet sump question?

marshg246 said:

You will get lots of answers. I have two depending on if you have a reed valve breather. With a reed valve breather I don't even look I just start the bike. Yes, there a chance that the main seal could still be pushed out, which would be a PITA, but I don't consider that very hard to fix and it's never happened to me. Without a reed valve breather, I drain the sump if I can see that the oil in the tank is down to the screen.

One of my bikes wet sumps fully in two weeks another in around 5 weeks. Both have reed valve breathers and I simply start them.

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When you say 'reed valve breather' do you mean any reed valve breather or one of the ones mounted on the sump which actively scavenge excess oil back to the tank?

Time Warp said:

Don't overthink it.
This might have been the idea of Ewan Greenforest.

View attachment 96520

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Won't work...see siphon effect for details ;-)

Tom P said:

When you say 'reed valve breather' do you mean any reed valve breather or one of the ones mounted on the sump which actively scavenge excess oil back to the tank?

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cNw, cNw for 1972, NYC, and any others connected to the sump and actively involved with crankcase breathing. I have no idea of the value of any reed valve breather attached anywhere else, but I should have been clearer.

Tom P said:

When you say 'reed valve breather' do you mean any reed valve breather or one of the ones mounted on the sump which actively scavenge excess oil back to the tank?

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Yes, I can vouch for the NYC being plug and play, and is a very nice piece of kit.

I have just drained the sump after two weeks on my 850 mk3,I got 1.6 litres/2.8 pints out.This is my first Norton but it seems like a lot of oil to me.I guess it’s time to have a look at the oil pump.Also,can the anti drain valve on a mk3 stick open and allow the oil to pass?

Not sure about the mk3's, but the mkIV oil pump gasket and timing cover gasket need to be properly matched for thickness so the oil pump output rubber nipple seals as it should against the timing cover port. That is, if the oil pump is removed for servicing if one decides to go that route.

I have a MKIII. Long ago and far away I did a mod to the check valve that involved lapping the plunger against the seat. The boss told me it wouldn't work. It leaked before, it leaks now. I just look in the oil tank with a flashlight to see how much oil. Generally, it will leak a couple of pints over the winter so I just consider draining the sump part of spring wake up. When I rode all year it wasn't an issue.

Trophydave said:

Also,can the anti drain valve on a mk3 stick open and allow the oil to pass?

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Yes, the Mk3 anti-drain valve can stick open, however, even when it doesn't, oil can still potentially drain from the feed side of the pump to the scavenge etc. so the anti-drain valve alone won't necessarily prevent the oil from draining without the pump shaft O-ring modification.

The Mk3 pump seal (not the same as pre-Mk3) also needs to be in good condition and the timing cover gasket must seal the return gallery in the crankcase even though the Mk3 pressure relief system doesn't use it so it can be blanked off (as the 2nd. pic in the linked post).

Trophydave said:

I have just drained the sump after two weeks on my 850 mk3,I got 1.6 litres/2.8 pints out.This is my first Norton but it seems like a lot of oil to me.I guess it’s time to have a look at the oil pump.Also,can the anti drain valve on a mk3 stick open and allow the oil to pass?

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I had 0.75L in just under 4 weeks on my mk3. An unusual lack of use, I was away on holiday! But gave a good chance to measure it. I have the modified sump plug from AN, so easy to empty the sump without risking the threads in the case.