scavenging oil

I have a 1957 99 and I feel it is not scavenging properly after draining sump and going for a 5 mile run there is 300mm of oil in the sump, how much should there be? It has a new six start pump should some of the oilways be enlarged? The flow back into oil tank is continuous indicating it is not keeping up with oil flow into engine, crank seal looks ok and seal to pressure valve looks ok also,what is the bolt below pressure valve for ,is this just to block off oilway drilling? what else should I be looking for? any help appreciated.

I hope you mean 300 ml.

What are the actual symptoms, as you ride the bike? Is there a lot of smoke, or oil escaping from the breather?

I have no idea what bike you have but 300ml = less that a can of beer maybe a cup of oil in the sump... Not much in the big picture... My commando engines have that "about" if i drain the next day!! .... There is a lot of surface area that clings onto oil and will take several hours to hit the sump...

If its pumping to the oil tank whilst running and there is adequate oil pressure.............. Happy days!!!

It is good that the flow back into the oil tank is continuous. If it is not, then you have a problem!

Glen

I have never seen a dry sump engine with a continuous return. The return side pump is always of a greater capacity than the feed side to ensure the sump remains dry. This inevitably leads to an intermittent return feed. Sometimes it takes a minute or two from start up if wet sumping has occured.

Sorry I do mean 300mls of oil in sump,The flow back is a steady stream as stated previously isn't it supposed to become intermittent after a while? it isn't doing this if I keep running bike it burns oil I'm sure this is not because of worn rings or bore I have rebored and replaced rings,I feel there is too much oil in sump being thrashed around forcing it past rings,also excess oil is being expelled from the breather,another thought I have fitted an external oil filter (same as commando) could this restrict flow back to oil tank enough that pump can't catch up? although I cant see how this is possible when pump is supposed to pump is geared to pump more back into tank than it pumps to engine I'm still lost here any thoughts?

When you changed to a six start oil pump gear did you do any other mods to the engine? If you still have scrolled rocker shafts you may be over oiling the top end.

The bolt below the pressure relief valve is a plug for drilling.

My Atlas has always (I've owned it from new) returned a steady stream of oil . Yes, one would expect an intermittent stream if the scavenge side of the pump has twice capacity. The fact that the stream is steady suggests the stream is frothy with air on a continuous basis.

300 ml of oil in the sump is most likely splash oil which drains to the sump after engine shutdown, as well as drainage from the head. I would not worry about it.

Slick

If the scavenge side can't keep up, then the sump level would keep rising !?

Changing to the 6 start pump would be potentially putting a lot more oil through the crank,
so the scavenge would need to be doing more scavenging, hence the stream of oil. ?
Also, the pressure relief valve just bypasses a lot more oil....

Can you see when it burns oil ?
Is it all the time, or a puff of smoke on the over-run, or on startup.
Its not just blowing it out the breather, is it ?

Someone somewhere mentioned oil rings fitted upside down, which is always a problem,
pushes the oil up into the combustion chamber.
Are the plugs oily or fluffy black - a sure sign of burning oil.

I've always understood that the scavenge flow back to the oil tank has a large part of air included, up to about 30%. Certainly when designing an oil tank for something like a Commando, the capacity of the oil tank is determined by the required oil capacity (say 4 pints, whatever) + 30% for the froth.
No doubt others will disagree!
cheers
wakeup

wakeup said:

I've always understood that the scavenge flow back to the oil tank has a large part of air included, up to about 30%. Certainly when designing an oil tank for something like a Commando, the capacity of the oil tank is determined by the required oil capacity (say 4 pints, whatever) + 30% for the froth.
No doubt others will disagree!
cheers
wakeup

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I agree, but the air returned with the oil stream should vent thru the oil tank's vent, but may carry with it a significant quantity of oil. Therefore, some means of mist control or oil scrubbing should be part of the oil tank's vent system.

The scavenging side has greater capacity but the pressure side pumps continuously at a given rate. Once the scavenging side has the excess oil out of the sump, it pumps at the same rate as the pressure side in order to maintain the level.
It has to.
Just like a sump pump that pumps forty gallons a minute placed in a pond that has an inflow of 10 gallons a minute. Once it sucks the pond down to the level of it's inlet screen, it pumps an outflow of 10 gallons per minute.

Glen

Took off timing cover ,crank seal looked suspect so replaced also checked pump too looks fine,had my doubts about conical oil pump seal ,has gasket between pump and crankcase,previous seal had no shims behind it only had a spare mk3 seal to fitted that . Started bike continuous strong flow for a minute or so then intermittent flow,will take for a run tomorrow if I get a chance and report back. can anyone see a problem fitting mk3 seal??

mark375850 said:

Took off timing cover ,crank seal looked suspect so replaced also checked pump too looks fine,had my doubts about conical oil pump seal ,has gasket between pump and crankcase,previous seal had no shims behind it only had a spare mk3 seal to fitted that . Started bike continuous strong flow for a minute or so then intermittent flow,will take for a run tomorrow if I get a chance and report back. can anyone see a problem fitting mk3 seal??

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The shims behind the conical seal are to press it against the timing cover. When fitting the timing cover, the cover should stand off the seal...that is, there should be a small gap between the cover and the timing case gasket due to the conical seal pressing the cover off. This gap should easily be closed by hand pressure, but should open when pressure is removed. Use one or two shims (or none) to get this effect. A timing cover gasket too thick will negate the proper gap.

There is no gasket between the oil pump and the crankcase. I just smear a very light coat of non-hardening Permatex on the pump face....too much can clog the ports. The oil pump nuts are torqued to 10 - 12 ft-lbs.

This is what the Norton Owners Manual states:

Reference: Norton Owners Manual (no date of pub.)
The following statement is found under Heavyweight Twins, and Models ES2 & 50

"Engine Oil Pump.
This is of the gear type. The pump contains two pairs of gears, one on the feed side and the other on the return side.

The gears on the return side are twice the width of those on the feed, having twice the pumping capacity. This ensures that the crankcase is free from oil when the engine is running.

......After the engine has been running for a few minutes, the oil return flow will be spasmodic, due to the greater capacity of the return gears."

Slick

fingers crossed I think I might have sorted it oil return really strong,stronger than before i changed seals,then intermittent I'm thinking seal leaking back into timing cover so pump although pumping was loosing some back into timing cover and what was returning to tank was less than flow from tank to engine hence after a run there was too much oil in crankcase oil being flung everywhere rings couldn't cope and crank fighting the bath of oil it was in.Bike seems to rev a lot easier. anyway that's my theory,will continue to run and hopefully that will be the end of it

texasSlick said:

There is no gasket between the oil pump and the crankcase.
Slick

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There can be though. There is one produced and to compensate for this a thicker timing cover gasket needs to be fitted.