Oil Consumption

[belfastguzzi]

Why V11's are particularly prone to this and what I'd suggest are sensible solutions are something I can rabbit on about later but only if anyone is interested

Pete

54288[/snapback]

"There was nothing so very remarkable in that; nor did Alice think it so very much out of the way to hear the Rabbit say to itself, `Oh dear! Oh dear!"

 

– please do on

[Guest ratchethack]

Why V11's are particularly prone to this and what I'd suggest are sensible solutions are something I can rabbit on about later but only if anyone is interested

 

Pete

54288[/snapback]

Pete, by all means please continue with comments on causes and solutions. I've got 2 riding Pals with V11's with intermittent flickering oil light symptoms - one's a Sport and the other's a LeMans. I think the entire Forum would be most interested.

 

Many thanks in advance!

[Baldini]

.....Why V11's are particularly prone to this and what I'd suggest are sensible solutions are something I can rabbit on about later but only if anyone is interested ...

 

...if you insist Pete,

 

Not sure what good oil consumption should be. Wonder how it varies with running in procedures?

 

KB

[belfastguzzi]

It's not so much the oil consumption, as what the oil does / where it goes when in the engine and particularly the sump (under particular circumstances?). It looks like the low oil pressure problem is widespread.

[Baldini]

Just checked mine - after bit over 650 miles it took a little under 200cc to bring back to max on stick, which seems about same as usual.

 

Long time back, this problem was discussed on Centauro site - think one solution was keep filled to max (& beyond!). But that's no solution if the bike won't hold max.

 

I know there are some might think i should keep my mouth shut when it comes to levels of fluid intake but .....you sure you are making consistent measurements? I do engine run from cold a minute or so, bike vertical, dipstick screwed home....& fill to max mark .........except Friday nights when the lines can become a little blurred

 

From partsbook engine breather system seems simple: Pipe from crankcase (clutch end) to bottom rear of headstock vents crankcase pressure to frame. Pipe from top rear headstock vents air (maybe some oil mist) to airbox. Pipe at bottom left rear of spine drains any oil settled in frame back to sump. There appear to be no valves in the system (Tontis had a couple of one way valves that could stick causing problems). There appears to be no vent to atmosphere. So if oil isn't being ingested, burnt or leaked it's hard to see where else it could go.

 

My guess is oil is going thru intake side when high speed use builds up c/c pressure.

 

KB

[Guest aironepony]

So far............so good.

 

2000miles since last fill, no appreciable drop on dipstick, no flickering oil light. Maybe I'm too gentle; my nephew says that I ride "just like a policeman". I'm pretty damn sure that's meant as an insult (he's rushing about on a Honda 600 something something R/R that's covered in tupperware).

 

..................................

[Baldini]

.....I ride "just like a policeman". I'm pretty damn sure that's meant as an insult .....

 

hey Martin! you should get together with nephew: think he needs ejukatin......

 

KB

[Martin Barrett]

[pete roper]

OK, first though a couple of caveats. These observations and suggested cures are based on my 1/4 century of farting about with Guzzi twins. They should NOT be taken as definitive answers but are purely my ideas and suggested ways of fixing what I have percieved as a long time Guzzi failing.

 

To start with in any major way the actual Guzzi block has changed very little in 30 years of production. Essentially it's internal volume has remained the same from the V7 of 1967 right up to the current V11 series. What has changed marked ly is the swept volume of the motor. Up from the original 700cc to 1064cc. that's over a 30% increase. It's important to remember that the swept volume is not only above the pistons it's also below it and while the diference between the crankcase's maximum volume, (When the crankpin is at 12 O'clock.) and it's minimum volume, (When the pin is at 6 O'clock.) is not that full 30+% it is still a healthy increase so the amount of change ot the *air volume* in the case between it's maximum capacity and it's minimum capacity has increased appreciably so every revolution it has to cope with trying to push more out and overcome the tendency to try and pull more back in with a V11 than it did with a V7.

 

The bore size has likewise increased from the original V7's (?) 80mm to the current V11's (?) 92mm This makes the circumfirence of the bore larger, (251mm Vs. 289mm.) which means there is a greater area that the rings have to seal. While with the advent of Nicasil bores this is less of a problem than it could be it's still a big step and it's noticeable that models with cast iron bores are a lot more prone to pressurising their cases later models have only 1 and 1/2 compression rings as opposed to the earlier models 3 and new bikes use semi-slipper pistons with a truncated, and shorter, skirt that are more prone to rocking in the bore hindering ring seal.

 

Another factor may well be the longer stroke of the later models. This places the rods, crankpin and webs closer to the surface of the oil in the sump so the cyclonic forces it creates, (Remember, it's spinning 100 times a second at 6,000rpm!) will have a greater chance of dragging oil out of the sump via windage and keeping it in suspension in the *air* within the case.

 

Lastly it should be remembererd that the V7 as a low compression, slow reving slug. Despite it's shorter stroke it was never really designed to be taken much over 6,500RPM. Yes, you can do it but it will achieve bugger all apart from making it sound like a cement mixer full of bricks! You'll still have to use time-lapse photography to establish whether the horizon is coming towards you .

 

Remember too that there is always going to be *some* leakage of gas past the rings and usually a small amount past the guides so over the 720 degrees of the cycle, especially once the motor is spinning fairly fast and is under heavier load the crankcase is always going to have a degree of positive pressure when compared to atmospheric as *some* leakage into the case will occur on every power stroke. It's gotta go somewhere, hence the breather system with a vent to atmosphere, (Or in the case of later bikes a vent into the airbox to re-breathe the escaping hydrocarbons.).

 

That is basically the reasons that they pressurise the crankcase and consequently try and blurt their oil out.

 

I gotta go off and do some work now, (I do, occasionally do this, I'm not at the wretched 'Pooter 24/7 ) but I'll come back later and discuss the lubrication and breathing systems before making my suggestions as to what can be done to help.

 

Pete

[belfastguzzi]

I'm hooked. Same time, same place on the dial tomorrow?

[pete roper]

OK, on to the lubrication and breather systems.

 

First and foremost you have to realise that THERE IS NO SUCH THING AS *SUCK*! This should be drummed into every first year apprentice with a rod of iron as so many misconceptions about the way stuff moves relate to things being *sucked*. What any pump, be it the oil pump or the cylinders do is create a low pressure area. The greater pressure from *outside* then pushes whatever is being pumped into the lower pressure area. It doesn't matter if its the gaps between the teeth and body of the oil pump or the cylinder as the piston decends, what is happening is that a low pressure area is being created and *Something* with more pressure pushing it will rush in to occupy the low pressure area.

 

With the twin-gear type oil pump as used in your V11, (Or any previous big Guzzi twin.) what happens is that as the gears un-mesh they create a low pressure area between the teeth. Pressure in the crank case forces oil into the space and it is then carried around the outside of the gear in the gaps between the teeth and the pump housing until it is squeezed out again by the teeth on the delivery side meshing again. This makes the delivery side pressurised so it seeks an escape route which it finds through the galleries to the various bearings and thence to the inside of the crankcase. This obviously takes energy which is provided mechanically by the motor and actually robs the motor of power. So, if you want more power, (For a nannosecond or so!) remove your oil pump! Simple, innit!!!!!!

 

The thing is how does the oil get to the pump? Well, obviously it isn't *sucked*, (I hope you're paying attention up the back!!!!!!) It gets pushed by the pressure inside the crankcase which will be atmospheric, (14PSI/1 Bar.) plus a bit from whatever high pressure gasses are leaking past the rings and exhaust valve guide. Now quite simply that isn't much pressure, at least not in *real* terms. and it's trying to push a fairly viscous liquid through a fairly small hole, yes? This is the main reason its NOT a good idea to thrash your engine from cold. When the oil is cold it's more viscous, (Thicker, yes?) so it's going to be a lot less willing to be pushed through a pick-up or gallery by the weedy 17PSI or so in the case. If the oil is *thick* enough what will happen is that as the oil pump gears spin there simply isn't enough time for the space between the gear teeth to fill up with oil so less is delivered. this is what is known as 'Cavitation' and what happens is the pump is effectively pumping *empty space*. Needless to say this empty space provides bugger all lubrication or cooling so your bearings go tits-up! Make sense??????

 

 

This is something that designers will take into consideration with an engine when they first set about drawing it up and while most Guzzis won't have a problem if, like me, you set about building a motor that will rev to 10,000RPM you soon discover the limitations of the standard oil pump. My little hot-rod used to torch it's big ends lavishly and with Gusto when I abused it but, unforunately, it was such FUN to abuse I did it often. It gets old very quickly mind

 

So lets go back to the beginning and the V7 through to the 850 T. These motors didn't have an oil filter. Just a strainer on the pick-up to take out the *lumps*. This was bolted to the back of the front of the crankcase (???) and essentially was a bit of bent pipe that stuck down into the sump below the level of the oil. Now lets face it, and I'm sure that Jason would agree, (he has an Ambo.) Those early models wers scarecely fire-breathing monsters that would accelerate so hard that the oil would be liable to slosh towards the back of the sump under acceleration!!!!!! 'Dignified' is the term usually used to describe the performance of these early models and despite the pick-up being at the front of the sump it was unlikely that it would ever be exposed, even under the most extreme, beetle-browed, nongish shows of enthusiasm by their owners. Remember of course as well it was originally designed for the police and military, principally for escort work which is hardly 'Nose on the Tank' stuff!

 

Presumably once the 850 T came out and performance went up a bit,(oh, and the poxy V7 Sport that everyone raves about!) exposure reared it's ugly head. Oddly enough even the earliest crank cases have the cast in bosses for the later oil galleries that were used from the T3 onwards which allowed the fitting of a different sump with a fairly central, bottom mounted pick-up, (Still covered by the 'Lump Extractor') and a different, slightly higher output, oil pump on the crankcase. Post T3 bikes all had this sump which also allowed, for the first time, provision of a *real* cartrige type oil filter. This was located within the sump and required the removal of the sump to change. Remember that. It's important and you'll be tested on this later! This competely cured the pick-up exposure problem but created another one. Namely that Guzzi owners started pissing and moaning about having to remove the sump for filter changes . An added down side was that it made the path through which the oil had to be pushed more restrictive, but having said that I've never found it a problem apart fro m on race engines and guzzi eventually tackled it by increasing the size of the pick-up gallery from strainer to sump on the 1100 models, (Maybe before, can't remember.).

 

This system worked spendidly for a couple of decades but during that time the whining, carping and general stupidness from owners, (Most particularly the Yanks!) about the removal of the sump to change the filter reached a creshendo and rather than payingb a royalty and addopting the 'Harpers Outsider' solution that had been around for years they chose to design their own solution. This first crawled out from under it's rock with the Daytona RS/Centauro Sport and Sport Corsa models which were the first to have the 'Broad Sump' as fitted to the V11 series machines. At Last! Here was an answer to the whiners prayers!!!! In the bottom of the re-designed sump there is a fucking great plate with a 27mm hex in it. Around then outside it has a flange and O-ring to seal it and then a very, very fine pitch thread that screws the plate into the sump. This piece of incandecent brilliance not only is prone to seizing the threads, (especially in cold climates where they put shit on the roads in winter) and is easy to cross thread, necesitating a new sump and plate, but it requires a 27mm hex tool to remove, (Hands up how many shops, never mind home mechanics have such a silly thing ? I had to get one made!!!!!) and it's crowning glory was that even when you got the bloody plate off you STILL couldn't get to the filter without a special filter wrench and 9-times out of ten IT would slip off the oily filter before it came undone so you have to remove the sump anyway!!!!!! Hoorah!!!!!!! Well done boys and girls! What a waste of money and a complete frontbottom of a job has been made of something that was previously so simple!!!!! 10 out of 10!!!!!!

 

 

Now, to fit this horrid excrecence to the motor required bolting a nasty bit of plumbing to the inside of the crankcase to hold the filter, and, incidentally, the oil pick-up from the sump. The one other thing it allowed was the fitting of a thermostatic control for an oil cooler which is all well and good but apart from with the Hi-Cams which run a lot hotter it's, IMHO, about as much needed as a saddle on a Unicorn!!!!!! The problem is that the oil pick-up has reverted to being a forward mounted *pipe* that just pokes down through the strainer into the sump so it revives the old problem of exposure during hard accelleration. The problem is that these later models like to go!`An Ambo they aint!!!!! Hence the problem with flickering oil lights!!!!!!!!

 

You may of noticed that i haven't mentioned the sump extension fitted to post '82 models? The reason for this is that it has more to do with the breather system than oil delivery and that guys, is the topic for the next little rant!!!!!

 

Pete

[Guest Lash]

That's what I was thinking/hoping, so, we'll believe it to be true.

Mr Baldini got a try on the 1100 Breva at rally. Apparently it's a great bike. Pity it's as ugly as sin. I think I'd rather look down on a flickering oil pressure light than the Breva's ever-expanding-fueltank/plastic thing and the spacehopper ear handlebars. And what will it be like in 20 year's time, sitting at the Erin rally with your classic old Breva, a multi-meter and a penknife trying to bypass the fizzled-out whizzy electronic start-up diagnostics so that you can get the old crate home?

 

Anyway, back to oil-levels. Baldini likes to keep topped-up. But don't mention it. Shhh..

54032[/snapback]

 

"Shades of Future Passed." Don't you love the Moody Blues? So appropriate for Moto Guzzi.

[pete roper]

OK, (Sigh!) Nearly there.

 

The breather system.

 

We've established that the larger the displacement of the motor the greater the pumping action as the pistons rise and fall so the greater the pressure differential between the case *maximum* volume and it's *minimum*. Now lets look at the effect this may have and how the factory has tried to cope with greater or lesser success over the years.

 

The crank whizzing round in close proximity to the oil in the sump will have a tendency to pick up oil particles and droplets from the sump and drag them around in the low pressure vorticees behind the crank webs. oil flung off the crankpin through the spray jets fitted to some connecting rods and the side clearance of the rods will also tend to remain suspended in the air within the case until it hits the walls of the case and runs down returning to the sump. this means that there is always a mist of oil floating around in the air inside the case and this will be pumped out of the breather along with the excess gas towards the low pressure area outside, (The atmosphere.).

 

Initially Guzzi used a collecor/condensor box that was not really much more than a small box stuffed with wire wool. The expelled gas/oil mix went into this via a one way flapper valve in the inlet and the oil particles condensed or were deposited on the wool and then drained back in liquid form to the sump via a return pipe. this at least was the theory. In practice, especially with the larger displacement motors with cast iron bores, the fact that the return pipe returned the oil to BELOW the level it was supposed to be in the sump it was possible under hard running for the crankcase pressure to actually push the oil from the sump back UP the return pipe, flooding the condensor and then puking it out of the breather to atmosphere or in the case of bikes with a rebreather system filling the airbox until suddenly oil flooded down the inlet trumpets, through the carbs and flooding the motor, (Guess how I know this?).

 

To combat this problem Guzzi started fitting a sump extension, basically a one inch spacer, between the block and the sump itself. This had the dual benefits of not only moving the oil away from the spinning crank but also increasing the volume of the case so the pressure varaition was reduced during the cycle aiding the dimunition of the pumping action of the cylinders. On later 1100 Cali models the sump extension has been replaced with a much deeper sump but the overall outcome is the same. They have also over the years replaced the original, and horrid, flapper valve in the breather box with a ball valve and routed the oil returns in various different ways to avoid the pumping back into the condensor problem.

 

With the advent of the spineframes the condensor has become the spine itself. the big box-section of the frame has the crankcase breather run into it, (without any sort of ball valve, (Commonly known as a PCV, Positive Crankcase Ventilation, valve.) in the system to the best of my knowledge. The greater volume of the spine allows for a greater area for the oil vapor to condense and it then runs back down the spine and is returned to the engine via a pipe or pipes to the sump or drain plug for same. The excess *gas* is vented intio the airbox for re-breathing through the motor. To the best of my knowledge the V11's don't suffer from the problem of crankcase pressure pushing oil up the returns into the airbox but the fact that a lot of people suffer oil loss with no visible sign of leaks would seem to indicate that the oil is going *somewhere*. Where I don't know for sure but I'd think that the absence of a PCV valve between the case and condensor may well mean that a lot more oil is expelled into the frame than was expelled into the condensor boxes of earlier bikes. It may well be that given the throughput of gas through the breather system the oil simply doesn't have a chance to condense out as it should and conseuently more of it passes through the re-breather system and is simply burnt by the engine. While this is not enough to cause any obvious indications like crusty plugs it *may* well contribute to detonation as a clean charge is much less likely to detonate than an oil contaminated one.

 

So as to oil *loss* I don't see this as a problem per-se. It's just a consequence, and a fairly minor one, of grossly over-stretching the original design parameters of the engine.

 

What IS a concern is that as a result of this loss the level can easily drop to a point where, under certain circumstances, the pick-up can be exposed and this, as discussed, is BAD NEWS!!!!!

 

So, finally, what can be done about it?

 

IMHO the first step, which is unfortunately the most expensive, is to ditch the broad sump and it's spacer and pick-up and fit one of those German V sumps. Not only will this move the oil further from the crank but it re-locates the pick-up to the very BOTTOM of the sump where it is less likely to be exposed. Yes you loose the provision for the oil cooler but as I said on a pushrod motor terms like 'Tits on a Bull' and 'Ejector Seat in a Helicopter' come to mind, especially on a road bike.

 

Secondly I'd fit some sort of windage tray/baffle plate to separate the oil in the sump from the spinning crank, in effect 'Dry Sumping' the engine. While Enzo has addapted one of my plates for this purpose and still uses his 'Broad Sump' the nice thing about using the V sump is that the windage tray would be child's play to manufacture as the only holes needed in it would be those for the bolts to hold it on and slots in it for oil feed, pick-up and return, the filter is of course out the front and I don't Think the pressure relief valve would poke up high enough to foul he plate.

 

For those wishing to minimise loss of oil, (and therefore refilling.) fitting some sort of windage/baffle plate would certainly help prevent the rearward surge of oil under hard accelleration and the consequent risk of pick-up exposure as well as reducing the tendency of the crank to draw oil from the sump whilst spinning therefore giving the the entire breather system an easier time and hopefully preventing quite so much oil being breathed through the motor. For those unwilling to take the step to the V sump Enzo can probably supply the patern of the plate he's using in his bike.

 

The other alternative is, I suppose, to ride your V11 like an Ambo but i can't see too many owners coming at that!!!

 

As I stated in the first place this is all my own personal theories, they may be quite wrong! Having said that while my experience with V11's is minimal I've found that similar issues with earlier bikes could be addressed in the above mentioned ways with considerable success. If you follow my train of thought and understand how the various bits work and what they need to work properly you'll find it all make a bizzare sort of sense. Having said that I'm *really* glad all mine are 1980 models

 

Pete

[Guest aironepony]

Pete,

 

A masterpiece of analysis. Many thanks.

 

This would explain my earlier comment...."2000miles since last fill, no appreciable drop on dipstick, no flickering oil light. Maybe I'm too gentle; my nephew says that I ride "just like a policeman ". "..................................

[Guest Nogbad]

Pete,

 

Yes, I agree completely with your analysis. However, it leads to the inescapable conclusion that the V11 "Sport" moniker is tantamount to misrepresentation. Blimey, I sure don't want to prat about with expensive V sumps and windage plates and such like. I just want to ride it, occasionally hard.

 

I like the V11 ok, and it does have good pose value as well as handling nicely with adequate performance. Unfortunately I'm one of these odd bikers who doesn't get off on all that modification and customisation thing....

 

Something that attracted me to the V11 was the long 6000 mile service interval but stuff seems to go wrong more often than that for many people, negating the advantage. Mine has now done 4500 trouble free miles since the last workshop visit, so here's to crossed fingers. (Excluding the long overdue tranny recall which is now scheduled for the 7th July)

 

Talking of the tranny recall, I am still apprehensive that the bike will come back with leaks and potential problems caused by the work......