Wet sump starting dangers?

In a previous thread, I said that I've seen drive side seal letting about half a pint of oil going into primary, on a dommie which had stood for years. Now I have been in the position to strip that engine. I noted that the oil seal was worn and hard. It has also wear marks from the seal on the axle. So it might be the reason for the leak. Of course the large amount of oil in the sump made it obvious.

I have a Commando and an ES2.

If the Commando has wet sumped badly, by badly I mean most of the oil is in the sump, it is tough to start from cold but when started it soon returns the oil to the tank. No other dire consequences. It has a belt primary drive which obviously runs dry, so I would know if oil was getting past the crank seal.

The ES2 starts ok but you need to get going quick as it smokes a lot from the exhaust! Once it stops smoking you need to check the oil level in the tank as it will have burnt some. Again, no dire consequences.

Ian

If your engine has wet-sumped, make sure there is at least some oil in the tank.  The engine will have to run for a while before any oil gets scavenged back to the tank.  Especially if you have an oil filter - it may need to be re-filled by the scavenge pump.  Meantime, the valve gear and cam are not being fed.

If the engine has not run for a while, it's a good idea to make sure the cam is well oiled, and make sure the big ends have feed from start-up

Paul

The other not so well understood consequences are, Carboned up ex valves which can get sticky and burn out, sooted up spark plugs that don't have the same capability to clean themselves up now,resulting in misfires . Smokey exhausts that get interpreted as worn engine resulting in unnecessary stripdowns and basket cases!!.Puddles of oil under breathers. I'm rapidly heading towards a TAP.

It would be interesting to have a poll on those who have had problems and those who have not had problems known to be due to this but, as Robert suggests, there might be unknown unknowns!  I usually check to make sure there is at least about a cup full of oil - and top it up just a little, and fire it up and let it tick over slowly for a few minutes before raising the revs.

My shed hygiene standards (especially underneath the bikes) are too poor for me to be confident of keeping drained oil clean enough for re-use, so I suspect the risks and consequences of draining and re-filling are higher than those of just firing it up.

By the time you have done that you could have drained the sump! You can now get the large drain plugs which incorporates a smaller plug, which makes it easy. That is what I do in that situation. Why risk any other consequences? It only takes 2 minutes. Easy on a Norton, or an AMC; a pain in the b#tt on a Triumph, which involves removing 4 bolts and a sump plate....

Happily I have some long downhill runs from my house so I often bump the motor in a high gear and let it rumble along  at very low revs till the sump clears. After a few weeks layoff I drain the sump and return to the tank. Yet to see what the change to 10/40 Yamalube full synth will do. Have to take extra care not to get it in the clutch.

After 10 years of ownership I've come to the following conclusion regarding wet sumping...

It does wet sump when left for a few weeks and I just start the bike without too much trouble and allow the pump to do its work and return the oil to the tank. However the increased pressure in the crank case (when first started) means the I get oil escaping via the crank shaft / case seal and into the primary drive.

I've replaced the seal several times (easy to do) - but still get the same issue.

Every now and again I empty the primary drive and get half a cup of oil to clean out.

I've just accepted it as part of the running routine for a 40 plus year old bike.

Regards - Paul.

With two 850 Commandos both of which wet sump if unridden for several weeks , I employ two different approaches on each.

Kicking over the '73 Mk 1A with a sump full of oil is hard work so I ease the engine over several times on the kickstart to move some of it back into the return line until I can get a good swing going to fire it up and oil tank quickly fills - removing the plugs certainly makes the process easier but usually can't be bothered. Despite the extra crankcase pressure on start up engine oil has so far never found its way past crankshaft seal into the primary chaincase.

On my '76 Mk 3 fitted a Mick Hemmings anti-drain valve five years ago which has always worked perfectly although always check oil is returning to tank on each start up. Primary chaincase on this bike does get engine oil seeping past crankshaft seal so I drain off excess at level screw every 400 miles or so - usually get about 150 cc excess , but clutch operation is never affected.

When you first start, you will get some oil returning whether or not the automatic valve is opening as there will be some oil in the crankcase (drained down from the head etc). You really need to check after a few minutes when that has all been returned to check if the feed is OK.

Having said that, I had a Hemmings valve on my 850 Commando for several years with no problems. The key is to make sure that the pipe downstream of the valve is completely full of oil otherwise the pump tries to suck air and doesn't create enough of a vacuum to open the valve.

Velo singles have a similar valve fitted as standard and that point is stressed in the workshop manual.

Another solution is to use a big syringe after a ride. Take oil out from the tank, put it in a can, and wait for next trip to pour it back in the tank or, even better, in the engine by taking off the exhaust valves covers and lubricate the camshaft.

Or...

Ride your bike everyday.

I was advised to ensure the engine when switched off was in the compression stroke position, hence the oil has further to go to get into the sump.