Sudden Oil Loss

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Jul 1, 2008
Wondering if you guys can help me on something that just started happening the other day.

After having my 74 850 sit for a couple of days, I found about a litre of oil in my drip pan. I checked the oil level cold and it was just showing on the stick. It seems to be coming out of the primary chain cover gasket at the front. A large drip forms when it is sitting on the kick stand.

I was told that there is a wet sump on the bike and sometimes the oil pools in it. I started the bike, let it run a few minutes and checked the oil hot. It was halfway between the low and full mark. I ran it a bit longer and checked again and it was holding at the halfway mark.

I stopped the bike, added half a liter and after 2 hours checked the dripping again.

It had dumped another liter out same spot.

Ok so my question is what triggers the oil to go into the sump and does this sound like the sump is the cause of this?
'Wet Sumping' is caused by oil managing to seep past the oil pump internals and settling in the sump of the engine. It is a very common problem. Some people say that a oil pump rebuild will fix it but my experience is that even new pumps can still have the problem. With reference to oil leaking out of the primary drive gasket - do you mean the large rubber seal that goes around the entire chaincase or the paper gasket between the engine crankcase and the inner primary chaincase ?
It may be that the left-hand main bearing oil seal is leaking and if it's loosing that much oil so quickly I don't think you should ignore it !!

The screws that secure the inner primary chaincase thread into tapped holes that penetrate the crankcase. The lower hole will leak if the sump is full. A check valve will fix the problem. make sure that it is fully primed before you start the bike.
By primed, do you mean that there is oil in the oil pump? If so, I assume you would just make sure that there is some oil in the tank?

Don't mean it in a harsh way but. What he means is this. Think about this for a bit. Tank full of oil check valve in between the tank and the pump. You have stock looking black oil lines so you can not see that all the oil in the line above your oil pump has drained down while the bike sat. Now your oil pump can pump very well but it can't suck oil when the prime has been lost. So now your motor runs with no oil. for a little while that is. The one and only person who ran one that I new, had a clear line installed so he could see this problem the results of what he saw had him taking that Valve right off the bike. Do what you want you will anyway. If you do a search under my handle your will find a post that goes through the whole job with pictures right here in the archives. If you insist on valving it do it in the oil pump much safer.
By the way I know of several Norton's that have suffered sudden oil lost syndrome and it always goes back to a hone job that was done with the fine stones. The rings never seated. Oil control was also lost.
A half litre in two hours ? As someone years ago attributed to an old mechanic (In 'Bike' magazine, I think) - "That's not leaking son - That's pissing out"

I can't imagine how that much oil could flow so quickly past any sort of functioning oil pump. Have you had the timing cover off recently ? A damaged gasket could allow oil to flow directly into the timing chest.

It occurs to me that your engine could be drastically over-filled and is failing to scavenge and as a consequence has popped the drive side oil seal. Don't believe the manual when it says "Run the engine for a few minutes then check the oil" - it takes longer than that.

Have you tried removing the sump plug and the primary drive plug to see how much is actually in there ?
I apologize for the minor hijack here, but the 'honed with the fine stones' got my immediate attention.
I'm planning to pull my cylinders in the off-season to have them honed & fit new rings, is there a minimum "coarseness" of the stones that I should make the engine shop aware of? (I wasn't planning on honing them myself.)

220 is minimum 150 was used originally nether are found in shops nowadays only as roughing stones.
I agree with 79 X 100, that is a hell of a lot of oil to wet sump in such a short time. I would typically expect to find a pint in the sump after a couple of weeks. Sounds like something is not right.
Hi all. Norbsa's response is exactly what I meant. I recently rebuilt a 750 fastback motor. All internals were thoroughly lubricated for first start up. I got lucky on the timing and it started right up. My oil pressure gauge read 0 psi for a long 10 secs or so. The check valve had lost the prime and the pump was air bound. The lobes need to be submerged in oil to work. The motor is fine but only because of the pre-lube.

There is a newer check valve on the market with a clear plastic body to verify that it is in oil. Fitting any of the external checks is a job on a fastback due to the limited room for fitment.

Resolution appears to be changing the primary chain gasket and installing a anti-wet sump valve.

Thanks for all your assistance as usual.
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