Bubbling Oil - Can someone please explain?

[Sevorg]

For the past couple of weeks when checking my oil through the view glass I've noticed it's full of bubbles. Is it because it's getting too hot?

Bike temp, idle speed, running & general sound etc all seem fine. It's been serviced at all suzuki advised intervals. It's done 14k and will be ready for another service at 14,500 miles.

Should I be worried? Anyone got any ideas? It doesn't seem to be using any oil - Even after a couple of recent trackdays. :confused::confused::confused:

[SV-net]

Does it look like oil or is it more like a creamy sludge?

The oil will look like its bubbling as its being slopped about quite a bit even at idle rpm.

[Al_Sweetman]

Could it be because it's slightly too full?

[Alpinestarhero]

Is it like that after a short run...or a long run? If you are doing lots of short runs, it might have some condensation in it and therefore a bit emulsified?

[startrek.steve]

If youre doing lots of short journeys, your oil with build up water in it - making a creamy looking emulsion. Either change your oil, or go for a long blast to "Boil" the water out. The latter sounds better to me...
Sorry Officer, I was only boiling me oil!!

:smt036

[jambo]

Oil boils somewhere north of 350 degrees C. Coolant boils off somewhere north of 120 C, if you still have coolant in the bike, the oil isn't boiling.

The only time I've read of oil boiling was when a bike magazine held the throttle open on an F model ZX6R for about 20 minutes, stationary without airflow. They were destruction testing the engine at the time.

What does happen though is it gets nice and warm and runny, and then whisked up by the gears and whirly bits inside the engine, this adds a little layer of bubbles at the top of it, it's not a problem :cool:

[G]

Oil boils somewhere north of 350 degrees C. Coolant boils off somewhere north of 120 C, if you still have coolant in the bike, the oil isn't boiling.

The only time I've read of oil boiling was when a bike magazine held the throttle open on an F model ZX6R for about 20 minutes, stationary without airflow. They were destruction testing the engine at the time.

What does happen though is it gets nice and warm and runny, and then whisked up by the gears and whirly bits inside the engine, this adds a little layer of bubbles at the top of it, it's not a problem :cool:


I remember that test, didnt the oil boil nearly dry, until it clunked out.

They then topped it up with fresh oil and the bike ran fine again?

There is a pdf online somewhere with all the tests they did.

[jambo]

Soulkiss posted this a while back here (http://forums.sv650.org/showthread.php?t=111593&highlight=engine+test)

[Sevorg]

thanks all - The oil isn't too full it's just below the full mark. Plus, I don't actually do that many short runs. Usually 70 - 120 miles. You have all got me thinking though. I usually check the oil at the service station round the corner when checking tyres. It's only 1.5 miles away so perhaps I need to check when it's had a bit more time to warm up. The oil (although bubbly) still isn't dirty, in fact it's quite clean. I'll have a look for the Bike article. I've got a few yrs back issues.

Thanks for all your comments.

[Paul the 6th]

sev, mine bubbles when I rev it. I made the mistake of over filling it about 2 months ago, then spent 2 hours figuring out how to drain the excess away. Emptied it out a bit, then topped it back up to the normal level. That was when I noticed "oil bubbles" sat at the top of the oil level. When I rev it, the oil bubbles flicker and multiply/become small. Just like jambo said, when the engine is rev'd the mechanicals and gears pick up oil and slap it all around the engine to keep things nice and slippy.

If it is something serious, I've not had any problems. Where the hell is yorkie chris anyway? 10 posts and he's no where to be seen?! lol

paul w

[embee]

Presumably you're talking about visible bubbles in the sightglass either while it's running or immediately after shut-down.

As the others say, this is normal.

Oil aeration is one of the standard issues addressed during engine design/development programmes. It is a function of many factors, one of which is re-cycle time, i.e. the amount of oil in the sump vs the oil flow rate through the engine pump. The faster the oil is re-cycled the less time it has to de-aerate. Another factor is how close the oil is to fast moving parts (windage), which in a bike engine equals lots of rotating parts actually immersed in it in the transmission section.

In automotive engines a series of tests is done measuring the aeration vs the oil content of the sump, and usually you end up with a "U" shaped graph with a region in the middle where aeration levels are acceptable, typically a maximum of 5 or 6% by volume is the absolute limit set for max ovefill (often crank windage whipping up the oil) and min underfill levels (minimum is usually down to exposed oil pick-up when all the oil is "hung-up" elsewhere in the engine). The ideal running levels (max and min marks on dipstick) are then comfortably within the safe extremes, and typically aeration levels of about 3% are looked for.

Then the engine goes on a tilt rig ("rock and roll rig") and the tests are repeated at different tilt angles to simulate either hills or cornering/braking g-forces.

That's the simple version anyway.

[Al_Sweetman]

Cheers embee, that explains how they do it - I've always wondered had no idea it was quite that complicated!!

Another question - from my understanding, one of the major problems (apart from the increased pressure) in overfilling (in this case car) engines with oil was that if the bottom of the cranks dipped into the sump then it would make it all frothy and bubbly (akin to 'whisking') and it would cease to lubriacte properly?

I suppose there's different degrees of bubbling....

Al.

[embee]

Overfilling car engines with oil results in various things.

It generally increases the amount of oil whipped up by the crank rotation which increases the oil the breather system has to try to separate from the blowby gas.
It increases the drag (windage) on the crank, so reducing power (this can be easily measured and can be quite significant)
The extra windage tends to increase the aeration of the oil itself which can lead to various problems in the lube system itself, hydraulic tappets become soft, chain tensioners become soft, bearings can start getting cavitation problems etc

I usually recommend running oil at the mid level wherever possible, it's usually the best condition for the engine assuming the engineers have done their job properly.

[Alpinestarhero]

Embee owns :smt041

[custard]

bin told!

salute the mighty mechanical bod!

[startrek.steve]

Oil boils somewhere north of 350 degrees C. Coolant boils off somewhere north of 120 C, if you still have coolant in the bike, the oil isn't boiling.

I did actually mean boiling the WATER out of the oil... I do appreciate that oil does not boil in normal use!!!

Steve
:smt013

[SVGrandad]

I did actually mean boiling the WATER out of the oil... I do appreciate that oil does not boil in normal use!!!

Steve
:smt013
From memory, emulsified oil starts to release entrained water at about 140deg F, so a good thrash would probably clear it, as previously suggested.

[yorkie_chris]

Where the hell is yorkie chris anyway? 10 posts and he's no where to be seen?! lol

paul w

Here I am... but fairly useless anyway, as embee has hit the nail on the head.

[Sevorg]

yep - right on the head. Cheers Embee. I'll keep my eye on it. Off on a pretty big ride on Thurs so will be good testing ground. If you don't hear from me it's because I've broken down near Helmsley!!

[jambo]

I did actually mean boiling the WATER out of the oil... I do appreciate that oil does not boil in normal use!!!

Steve
:smt013
That comment wasn't actually aimed at you, more making a clear distinction between the various reasons people may think oil had bubbles in it.

Embee has, however, as ever provided a sound and clearly written summary of all the relevant issues. Stand up and take a bow that man!


Jambo

[Alpinestarhero]

various reasons people may think oil had bubbles in it.
Jambo

Just thought of another one:

Someone poured beer into your oil, and now those french blokes in that little bubble-making sphere are making bubbles

Just a hypothesis at this stage...

:D

[Devil Biccy]

Just thought of another one:

Someone poured beer into your oil, and now those french blokes in that little bubble-making sphere are making bubbles

Just a hypothesis at this stage...

:D

Winner!:eek:

[punyXpress]

Your engine is suffering from Fart in a Sauna Syndrome. :o