I am curious as to wet sumping being a problem, 1970 750s only gets started every other week .I would have thought that filling the crankcase with oil should do no harm, the only issue i see is it seems to make it a little harder to kick over( altho tihs could be imaginary or a cold engine V warm engine), I dont have any oil leak issues so is it something i should rectify with oil pump clearences ,valve in line or any of the other rectifications in my spare time..

It depends. I took the rpm too high too soon with a full sump and blew the crankcase seal (left side behind the alternator). It's a bit of a job to replace it, so since then I have been more careful and keep the revs to a max of 3000 until the bike has done at least five miles. This gets most of the excess oil out of the sump without blowing the seal.

Les Emery says that if the oil pump is in good shape and the bike is left on compression it should take 8 -9 months for the entire oil tank to drain into the sump.
I just read that tip today so I am trying it (leaving the bike on compression) to see if it really does slow the flow into the sump.

I'd say yes. I know on my 850 after it wet sumps I can look into the oil tank and the intake screen is visible and dry. This means there will be little if any oil pumping to the cam and top end upon first start, not until oil returns to the tank and the pump primes again. So....consequently I drain my sump and put it back in the tank before starting. I just can't run it with no oil going where it needs.

I agree that if the bike has wet sumped to the point where the entire contents of the oil tank have drained into the sump, it is best to remove the oil from the sump and dump it back in the tank.

I've never had my bike wet sump to that degree, maybe never let it sit quite as long, or it may be a difference in oil pump condition. Even with about half the contents of the oil tank in the sump, it is possible to blow the seal as I did. On the other hand, as long as there is still a couple of inches of oil in the tank, it doesn't seem to do any harm to run the bike at low RPM for awhile and let it pump itself out.

Les Emery is quite certain that it should take 8 to 9 months for the entire contents of the oil tank to end up in the sump, provided your oil pump is in good condition and the bike is left on compression.

Lube to the the crank is far more important than anything else.

Drain and re-fill.

I left the sump plug out of mine for a week and measured the flow. 136 mL in 6 days at about 20 Celcius, i.e. 23 mL per day. I'm sure it would be slower in winter, faster when it is hotter. This is with the pistons at TDC.

I agree, just keep the rpm down, to prevent excess pressure, until it has cleared, as long as there is sufficient oil in the tank to be above the screen filter to ensure the motor is properly fed. The excess oil will have one advantage - it will ensure the cam is well lubricated on startup.

If you have a 72 then it will clear quite fast through the breather, but at the expense of higher pressures in the crankcase. On others it takes a bit longer through the pump.

Yes it does - primarily to your passenger's shoes! My company hack 650SS had an oil drainage problem and I hadn't realised what was happening. Most of my bike experience had been on two-strokes, so I wasn't familiar with dry-sump 4-strokes.

I was going on a 200-mile trip, taking my wife along. Other folks had been using the bike for various duties. I checked the oil level, and found the tank empty. After a bit of cussing about lack of thought, I filled the oil tank up to the "FULL" mark.

Got home (about 3 miles), didn't see anything amiss, then took off on the trip. All the oil in the sump soon made its way back to the tank,added itself to what I'd put in and the excess came through the filler cap and onto my wife's lower legs and feet.

I was not a popular person, even after buying her new slacks , socks and shoes! Getting rid of the smell of used oil is very difficult.

Frank, You got me laughing out load Rolling on the floor with the wifes shoes story. The oil used at that time smelled indeed. Our new oil is tasteless by comparison.
My rule is simple if theres oil on the dip stick start and hold the RPM's down for a bit, if no oil on the stick, drain it.

Despite claims from some quarters that Nortons will not wet-sump if left at TDC on compression and with an oil pump that is within tollerance. I have never come across one that does not, regardless of the condition of the internals and the parking procedure. The various contributors to this thread seem to support this. I have recently fitted an anti drain valve from RGM and will monitor the efficacy of this device over the next few months. A friend had one fitted which didn't seem to help much.

Why dont you just start the bike and warm it up before riding off! Why would wet sumping harm any thing if you treat the bike correctly. Anti drain valves can prove fatal for engine life and if they were necessary why did NVT never fit them? Did you know that the engine oil in a Commando will need at least 15 miles in UK environment before it is anywhere near its correct working temperature. The moral is, treat it gentle until it is hot, its so simple. Some Commandos must weigh about 600lbs with all the unnecessary junk on them that the 'specialists' say you need!

I am quite familiar with the engine oil temperature requirements on Nortons, however I don't get out on my bike often enough and it wet sumps to below the level of the pickup in the oil tank, so currently I have to drain the sump and refill the tank which is a messy and time consuming job. Furthermore there are many improvements available from uprated disc systems to ignitions, suspension mods etc. that Norton failed to incorporate into the machines during their production run that are nevertheless improvements retro-fitted and enjoyed by many of us on this forum. I intend to try the anti-drain valve and see if it works for me.

There are many reasons why N-V might have not done something that was obviously needed. The main one was that they were financially bleeding to death, but there was also a big "Not Invented Here" syndrome which led to opposition to trying new ideas.

Dave use a clear hose down line of the valve it will scare you one day.

I think Norbsa is right. Oil from tank to anti drain valve will be prevented from seeping into the sump ok, but any oil downstream of the valve could still leak away past the pump and into the sump. Then, when you fire up, the oil pump has to suck on an air bubble in order to prime itself and get oil round the engine. Mosy of the time it managed this ok. But it is not without risk. If you fit a clear pipe downstream you can keep an eye on this a little better.

I intend to try the anti-drain valve and see if it works for me.

I'm afraid you'll be going from an annoyance to a potential disaster. You are putting an obstruction in the feed line to the oil pump with the inline check valve. I tried one of those easy fix gadgets. When the bike is warmed up, oil pressure was zero at idle. I took a few turns out of the spring, still zero pressure at idle. I chucked that valve under the bench. The proper fix is to send the timing cover and oil pump to AMR for their anti-sump mod. With the AMR mod the spring loaded check valve is on the output side of the pump. The oil pump is fitted with "O" rings to prevent it from leaking. Not to mention, with the feed line obstruction the pump has to prime itself every time you start the engine after any off time of more than a few hours, as Norbsa already pointed out.

I notice that some people on this forum insist on doing things that a number of posters have advised against, based upon previous experience. Two that come to mind are this inline anti-sump valve and the other is to not properly fix the crankcase pressure problem on the Combats. Changing crankshaft seals until they are dizzy when the problem is caused by too much crankcase pressure. Oh well!