Oil Consumption

[pete roper]

I don't mean to be argumentative, but I've seen 20 different failure modes on those switches, including flickery operation, and you're still assuming cavitation.

 

 

 

Nah, I don't reckon it's cavitation, I reckon it's exposure of the pick up due to oil surge rearwards. Cavitation is something else all together.

 

While I'm more than happy to be guided by Mr.Wittner I can't see how changing the way the engine inhales and exhales can have such a drastic effect. I mean more *oomph* should eaquate to better ring sealing, not worse?????

 

I'm certainly not looking for an argument, that was, I'm sure you realize, a joke. I'm just interested in seeing if there is a solution. It's interesting to note that on the late model Calis, (Dunno about the V11's?) the frankcase breather has been moved to the timing chest. The only reason I can really see for this, (apart from making leaky gaskets easier to fis, maybe?) is that there will be less oil being held in suspension in the timing chest rather than the crankcase.

 

Who knows? Not me for one, but I do know my old pusbags are remarkably oil tight. the only drips I get are from the 'Outsider' sump extensions that have sacrificed a bolt. I'm afraid i;'m still 'Old School' enough to refuse to use a gasket sealant on it

 

Pete

[twhitaker]

I would like to offer a suggestion as to why the spine frames sometimes suck air into the lube system and the Tontis do not.

 

Both have their inlets at the very bottom of the sump. They both draw the oil through the sump screen but the inlet on the spine frames passes through a hole in the top of the cover on the sump screen. There is an appreciable amount of clearance in this hole. When a bike rockets forward the oil in the sump lurches back exposing this hole. Air goes in this hole and is drawn into the inlet through a vortex which quickly goes away after the hole is recovered when the oil goes back forward.

 

One could slide an o-ring around the inlet pipe to 'semi-close' this area to see if the problem goes away.

[Greg Field]

OK, oil starvation, not cavitation.

 

That said, has anyone toasted their rod bearings yet? If these engines were truly starving for oil, they'd be roasting rod bearings. Seems the 1997 Sports, which are nearly 10 years old now and have the same oiling system, would be known for roasting rod bearings if it's happening. Me, I may be out of the loop, but I've never heard of it.

 

There's a Seattle guy I'm sure you've heard of with a V11 Sport, and he's ALWAYS accelerating at max capability and popping wheelies like a hooligan. Constantly. When I was inside his motor to put in a modified Roper windage tray and high-compression pistons, everything looked in top shape. Mebbe I'll add an oil gauge to that and see for myself whether they starve for oil, if no one else is gonna.

[al_roethlisberger]

OK, oil starvation, not cavitation.

 

That said, has anyone toasted their rod bearings yet? If these engines were truly starving for oil, they'd be roasting rod bearings. Seems the 1997 Sports, which are nearly 10 years old now and have the same oiling system, would be known for roasting rod bearings if it's happening. Me, I may be out of the loop, but I've never heard of it.

 

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This is not an indictment, or offered as evidence pro or con oil starvation, but to your question..... all I can say is that I had my oil light flicker a couple times, and when I had my cases replaced, they discovered one of my crank bearings was pretty scored

 

al

[belfastguzzi]

Here's how to test your breather theory: Detach the line to the airbox from the airbox, and stick its aft end in a big catch bottle.

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That's what I've done, as per the other (part 2) thread. So far, nothing has collected – to my slight surprise, but I need to wait a bit longer and do a longer run. I then want to move on to the other parts of the system.

 

I'm surprised if it's 'finely tuned' and if meddling with it will have dire consequences. But that's what I was asking about in the other thread. Thanks.

[Guest Nogbad]

Here's how to test your breather theory: Detach the line to the airbox from the airbox, and stick its aft end in a big catch bottle.

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This isn't quite a fair test. By simply detaching the tube from the airbox, you are changing the breather internal pressure as it vents to atmosphere now rather than having an applied vacuum equal to the air filter pressure drop.

 

Maybe it won't make any difference, I'm just pointing out that it isn't comparing like for like.

[Guest ratchethack]

There is an appreciable amount of clearance in this hole. When a bike rockets forward the oil in the sump lurches back exposing this hole. Air goes in this hole and is drawn into the inlet through a vortex which quickly goes away after the hole is recovered when the oil goes back forward.  One could slide an o-ring around the inlet pipe to 'semi-close' this area to see if the problem goes away.

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An interesting take, Twhitaker. I'm with you on the gap in the hole at the screen (which I've found a little suspicious myself for a different reason) but not quite able to follow you from there. Let's say you're able to seal this gap with an o-ring or some kind of sleeve. What would prevent air from then simply passing through the screen to get to the pickup, since we can safely assume that if the gap is exposed, the screen is also exposed?

[twhitaker]

The air will get in through the path of least resistance. The screen does put some resistance and the top of the screen is another quarter inch or so below the top of the screen cover. When I look at the two systems this hole in the top is the most obvious difference.

[big J]

Well,so far we have lots of theories and possibilities and maybe's, but poor old BFG is no closer to getting a good night's sleep. Can anyone say if a windage plate/sump baffle is available and works? Do the deep sumps help,or is there now so much oil in the sump that oil surge is worse due to the greater volume sloshing around? Would simply extending the pick-up pipe to within,say,6mm from the sump face work,perhaps augmented by a weir of some kind formed from something like devcon or plastic metal( havent dropped my sump yet, so dont know what it's like inside). On the subject of oil loss,it's a big air-cooled twin. If it doesn't get hot enough,you will get emulsification,simple as that.If you're going for a good run,check it before you go.If it needs some while you're out,top it up. It's an old design of engine,some will never use oil,some will use more than usual, get used to what yours does and work along with it to keep it happy. Just keep checking, it'll outlive your kids if you treat it right.

[Greg Field]

As for the pressure drop through the filter, I think it's insignificant, else your filter is clogged.

 

What Dr. John meant is that if you alter the relative sizes of any of the lines or get a restriction in any of them, from a twist or partial collapse in the line, or buildup of gumpucky, the whole system starts misbehaving.

 

For example, if the darin line is restricted, or the crankcase is pumping more oil than it can handle, oil can back up in that backbone, in which case the pickup is more likely to be exposed, and if it backs up enough, oil will flow out the line to atmosphere (to the airbox in this case). I've seen this latter scenario on my big-bore LM 1000. It was circulating far more oil through the backbone than the wee, dual drain lines back to the sump could accomodate that the backbone would fill up and then gush oil out the atmosperic line. It did this only at 90-plus-mph speeds.

 

The flickering-light problem could well be oil starvation. It could be something else, though, and your never gonna solve it until you know which it is. You guys have the tools in hand to figure this out. I don't have one of these bikes, so someone else is gonna have to do it.

 

As for oil consumption, that's solvable too, though the problem may not be the same in every case.

[Guest Nogbad]

I am dropping my sump to change the oil and filter this week, and will measure the distance between the pickup and the bottom of the pan accurately by bolting it up with a lump of plasticine in there and then taking it down and measuring the thickness of the squashed modelling clay.

 

I can't see the hole in the top of the strainer being significant, although a blocked strainer would be.

 

I shall swap from the existing 10W40 to 20W50 and will get the girlfriend to follow me in the car and look and sniff for burning oil.

[Greg Field]

Be sure to educate her on the differences in look and smell between oil smoke and gasoline smoke. . . assuming she does not already know.

[Guest Nogbad]

Be sure to educate her on the differences in look and smell between oil smoke and gasoline smoke. . . assuming she does not already know.

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Rats... There's always a problem.

[big J]

Good man yourself,Nogbad. Could you take a picture of the inside of the sump so those of us who havent seen inside have some idea of the relationship between pipe,strainer,etc?

[twhitaker]

There are several pictures on the previous page. The first one tells the story. To the left of the filter is a copper tube and to the left of that tube is the inlet spigot. From the looks of it there is only about 20mm of spigot sticking below the copper tube and that is all the farther the spigot can penetrate the hole in the top of the sump strainer. I'll bet there is another 5mm beneath the spigot and the bottom of the pan. Look at the dipstick. The oil level is probably 35mm above the top of the sump strainer. When the oil is sloshed to the back of the sump it's easy for me to see why there is some slurping and burping going on.