Why is my bike using oil???
 

My bike uses about a 250ml of oil a month.
I have checked the following : its not leaking oil anywhere
it doesnt smoke under hard acceleration
the exhaust is dry

So where does it go???

How old is your bike?

It is going to use a bit of oil if you rag it everywhere. Are you positive that it is not leaking anywhere. Mine weeps a little oil from the clutch cover. Don't really notice it unless you look hard.

Its a 2001 model with 26000Km on it.
I have checked the motor for leaks and its very clean...
I must admit I do bang it quite often... Our cops are still sleeping....

So if I hold it at 190Kmh for 20 kilometers it will use some oil...

yes

....................then explode! :wink:

As I've said (in other threads) before, mine uses about 80mls every 1000 miles or so,
I can stop that, just by slowing down and not hammering the bike so much, but I like doing :twisted:
(I recently went 2500 miles without any oil lose, just to try, bit borring though)

the SV lump is fine under normal use, but you have to expect a bit of oil consumption when you hack it.

Cheers Mark.

Rictus, where does the oil actually go?

Look in the airbox. It's from the two breather tubes that vent into the box. Designed mainly to vent gasoline fumes, but also allows oil to vent due to crankcase pressure. From what I've been told, it's a characteristic of twins especially.

vtour

That, and the fact the more you work the engine (higher revs) the more pressure there is, increasing the amount pushed past the rings,no doubt?

also the point of not letting the engine heat upand working it hard, would also send some passed the ringd before they expaned.

I'm only a practical mechanic, but I'm sure one of the techi boys will have a better explanation for you.


Cheers Mark.

You want one of these you do. There are still a few floating around on eBay I think. No oil leaks out of this puppy!!!

http://img96.exs.cx/img96/54/1076006...50_till02b.jpg

What does it say on the that cover in the dinky little picture?

Factory Pro

vtour

Breathers - the reason V-twins (and big singles, 360deg parallel twins, boxers etc) are significantly different to multi-cyl engines is that the piston motion means that the crankcase volume is cycling up and down greatly as the engine rotates. A 4-cyl inline engine "exchanges" gas between cylinders going up and those going down, as do other multi cyl arrangements (more or less).

This means that there is a lot of bulk flow and reversal in the breather pipes in addition to the actual blowby, which can tend to carry more oil mist. There also tends to be high pressure reversals in the crankcase, which can give more joint leaking problems than in an L-4.

However, oil consumption associated specifically with high speed+load is usually piston ring and bore geometry issues (generally termed "piston/liner interface). Particularly with the short slipper type pistons as in most modern bikes, the piston attitude (tilt) control becomes more tricky, and this can lead to ring lift off from the bore surface, or ring "flutter" in the grooves, which will dramatically (in relative terms) increase oil film thickness and thus oil consumption.

True "ring-flutter" is usually at high speed when you remove all the load (overrun or gear changes) and the gas pressure between the various rings causes the top and second rings to vibrate in the grooves, which drops the gas sealing and allows oil to get round the back of the rings. You often see a little puff of blue smoke when this happens.

Ring design is like most things a compromise of weight, dynamics, wear, friction and cost. The weight issue is a lot bigger than first sight suggests - one mm on the piston crown (ring pack) height means an extra mm on the height of the whole engine.

:shock: Farking Hell... Thanx....

Well guys there you have it... Always check your oil level before you start the bike just to make sure.....

...........oh and while on the subject, this is why a **proper break-in process is important, so that the surfaces of the piston rings, grooves, and bores are properly bedded together and so work correctly later in the life of the engine.

**proper means a process of progressively increasing speed and load over a reasonable time.......but others know better. :wink: :twisted:

Yeah, i have seen those, but it really ain't worth the outlay (for me) for such a little leak. Does look nice though.

Probably just wants a new seal, not a whole new cover- but any excuse to spend money :) If anyone ever spots the Yoshi ones, I've got first dibs...

I'm with you but there's no convincing some people. I don't know whether to laugh or cry when that link to that stupid irresponsible run in your engine by thrashing it website pops up.

Crikey! Go Embee!!
Thanks!

I don't know if bikes have the same issue as high performance cars but...

If you have an engine ina car designed for high performance and use it it should use oil. By letting just a little oil though you lubricate the cylinders to prevent excess wear. It wasn't unusual for the MR2 (2.0 Gti) I had to use enough oil for the oil light to come on midway between servicing. Others I know said this is normal for the cars.

My 2.0T Volvo also uses enought to go from Max on the dip stick to min in 15000km's, Volvo have said this is also normal.

Are bike engines designed in a similar way?

Stu

PS My '78 fiesta (first car) used to use an engine of oil every 50 miles, but that was a dead engine :)

it's what I do for a job, same as all you IT experts talk about your stuff. :lol:

Oil Consumption - Are bike engines designed in a similar way?
Stu

it's not that you really design an engine to use oil, and the theory that you allow more oil for bore lubrication is folklore.
It's simply that the higher the sliding speeds, rpm and therefore piston acceleration at reversal etc, the more difficult it gets to keep the ring pack under control.
You do design ring pack and piston grooves and lands (the bits between the ring grooves) to "manage" the gas leakage (blowby). You can use the gas pressures between and behind the rings to control the contact pressures on the bore and help to put off the point at which the rings lose contact with the bore.
Pistons tilt in the bore, typically reversing the tilt direction 7 times in a complete cycle. When this happens the rings slide in the grooves, and friction can make them stick momentarily. The tilt reversals are managed by offsetting the pin from the centre-line, typically a mm or so, usually towards the thrust side. This encourages the piston to tilt due to inertia forces at TDC and BDC, so you can get it sitting the right way before the firing pressure rises. This minimises the impact and thus noise.
You can make a ring pack work at very high speed but it necessarily ends up very light and slender, and durability becomes an issue.

A very significant factor in oil consumption is bore geometry. Bores are usually finish bored/honed (nowadays) with a dummy cylinder head bolted in place so that it's distorted just like when it's finally assembled. This means it's as round as you can get when the engine is cold, however they don't stay round nor straigght usually when it all heats up, so the rings have to accommodate a lobed tapered bore to some extent. This tends to give uneven oil film thicknesses round the bore surface and thus more oil consumption than you really need.

Emissions requirements tend to dominate engine development these days, and low oil consumption is crucial for long catalyst life.

my experience with oil consumption in my SV

if l check the sight glass religiously, and keep it topped off I go thru about 1quart-1½quarts between changes every 3500-4000 miles

however should I slip up and let it get below the sight glass, rate of oil consumption increases dramaticly. :shock: I have been almost 2 quarts low :oops:

heaviest rate of oil consumption is freeway steady high speed.

embee,

Question for you (slightly off topic sorry) would what you just explained be the reason MR2's suffer from servere piston slap until the engine has warmed up? Always remember them sounding like diesels for the first 10 mins or so...

Stu

My opinion is that most oil consumption is due to wear in the valve guides & seals

I spent a couple of years working on piston development in a family of car engines.
It's a complex subject, but yes, in basic terms the noise is from impacts of the piston on the bore at certain reversals. depending on which reversal is most significant you might do different things.

Pistons are very intricate objects, the skirts are not straight vertically, and they are not round, the ring lands are all different sizes and may be tapered and indeed need not be concentric with the skirt. Ring grooves have different back and side clearances. Oil drainage from the ring pack varies (internal/external). Pins are offset from the centreline (indeed pin bores aren't necessarily parallel, to allow for pin bending)

You try to get the profile so that it's suported by the skirt at all times, from cold starts at -30C up to full running temperature, allowing for the shape that the bore takes up too. However that can be difficult. The overriding requirement is avoiding scuff failures due to the skirt becoming too tight, and concentrating on optimising the contact area at normal working temperature. This may mean that cold start noise becomes an unfortunate compromise, though it's more and more unacceptable nowadays, and shouldn't be very noticeable in a well designed/developed engine.

The worst case is where the top land (crown) contacts the bore on the TDC firing reversal, that's the one that gives the diesel type rattle because the crown is very stiff and carries a significant amount of energy during the tilt due to the high rate of pressure rise.
If you can avoid the top land contact by extending the skirt support and altering the pin offset, you can turn a rattle into a "hollow growl", which is usually less objectionable. Most engines have some sort of piston growl from cold, in my experience. I've never known any mechanical damage from these sort of noise problems though, even in very noisy engines.
Emission requirements mean that top land clearance is kept to an absolute minimum (unburnt HC from "crevice volumes"), so it a close balancing act.

You can tweak cold start noise a bit by fiddling with ignition timing, but that's usually an emission/economy determined thing anyway.

Good block/bore structural design is crucial.

Modern valve stem seals are pretty good (actually metering devices, they are designed to control the oil flow not stop it completely), and unless they're damaged or completely knackered they'll contribute only a few percent to the overall consumption. Remember a piston is 10-15 times the diameter of a valve stem and slides nearly 10 times as far twice as often.

Breathers are usually no.2 on the list for oil consumption.