850 Wet Sump Problem

Hello, I know this has been covered extensively but I have a question. Once an 850 Commando has wet sumped can the engine be damaged by starting it without draining the sump and returning the oil to the oil tank. If so how does it damage the engine?? Who is the best at altering the timing cover to stop this problem??? I need to ship mine out to get the modification done. I am in Fort Worth Texas. My bike only has 3000 original miles on it and it sumps like a pig---In just one week. I am sick of draining the engine oil and want a good safe permanent fix. Thanks--

As I understand it, when the oil has collected in the sump, it's possible that there isn't any oil left between the tank and the pump (it's slowly dribbled into the crankcase), so at start up, the engine is operating without any oil for a few seconds, not until what oil is in the tank reaches the pump. This makes sense to me, as I was always told that start up is the most damaging to an engine, any engine, because the pump has yet to supply oil to the cylinder walls during the cranking process. It would appear this is made more likely in a Cdo engine with all the oil perhaps drained from the supply line.

slupdawg said:

because the pump has yet to supply oil to the cylinder walls during the cranking process. It would appear this is made more likely in a Cdo engine with all the oil perhaps drained from the supply line.

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With the mass of the crankshaft rotating semi-submerged in a sump full of oil at start-up, I wouldn't have thought lack of cylinder wall lubrication would be a problem, somehow?
'Wetsumped' Commandos tend to smoke on start-up-until the crankcase has had time to clear-so in fact there's probably rather too much oil thrown up at the cylinder walls? Logically it would be the big ends which would suffer most from lack of oil pressure, as the valve gear is unlikely to be affected by a temporary lack of oil supply.

Starting up with full sump has been known to blow the drive side oil seal out.

My Mk3 started after 7 days sitting and started on the center stand will smoke from the exhaust for a minute, but if I start it on the side stand it doesn't smoke at all.
I know it has drained nearly 1 litre into the sump in a week, but I figure that's a good reason to ride it at least every week. After 2 weeks I would drain the cases before starting it.
Why does it only smoke on the centre stand?
It smokes out the right exhaust.

graeme

I don't think the concern is so much the the cylinder walls, and maybe not even the crank as it will get spalshed. I'd be concerned about the cam myself.

When mine wet sumps, it will drain ALL the oil so that the oil intak screen and line are hi and dri. And as I understand it the return system on a Norton does not return it all that fast, So....your engine can run for a lot more than a few seconds without any oil going through it.

Like it or not, I always drain the sump if I can see the screen in the tank. Might be a pain but the old gal always rewards me with a wonderful ride afterwards.

lrutt said:

I don't think the concern is so much the the cylinder walls, and maybe not even the crank as it will get spalshed.

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I don't really see how oil from the sump could penetrate the plain big end bearings while the crank is rotating at 800+RPM? And the main bearings are adequately lubricated when the sump is empty so they're not going to be short of lubrication running semi-submerged?

lrutt said:

I'd be concerned about the cam myself.

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But the camshaft is splash lubricated? And with the crankcase half full of oil, it would be operating under more-or-less ideal conditions with all that oil being thrown about by the crank and rods-wouldn't it?

Mark Cigainero said:

Hello, I know this has been covered extensively but I have a question. Once an 850 Commando has wet sumped can the engine be damaged by starting it without draining the sump and returning the oil to the oil tank. If so how does it damage the engine?? Who is the best at altering the timing cover to stop this problem??? I need to ship mine out to get the modification done. I am in Fort Worth Texas. My bike only has 3000 original miles on it and it sumps like a pig---In just one week. I am sick of draining the engine oil and want a good safe permanent fix. Thanks--

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Even leaving it parked at TDC doesn't seem to slow it?

When was the last time the oil pump was surfaced?

I had the wet sumping problem so I fitted a vellocette type anti drain valve from Mick Hemmings, it was a doddle to fit and has stopped the wet sumping completely. Cheers, Steve