Crankcase Breather

[el-nicko]

Hi Mark,

..... until your bike decides to dump 200ml of oil at the side of your back wheel.

Hmmm, I'm just wondering if anybody has ever found 200ml of oil in their airbox. I doubt it.

[Blackal]

Hi Mark,

..... until your bike decides to dump 200ml of oil at the side of your back wheel.

Hmmm, I'm just wondering if anybody has ever found 200ml of oil in their airbox. I doubt it.

Just checked - found this!

[el-nicko]

Al, get sum therapy m8.

[Dai wiskers]

This is still on my to do list i have the filter here ready to go on next time i have the tank off i'm going to do this, it can only make sence to do it the BBS get cruddy in no time

If you do find 200ml of oil in your airbox you need a rebuild not this mod

Dai

[el-nicko]

If you do find 200ml of oil in your airbox you need a rebuild not this mod
Dai

.

[Dai wiskers]

It's at times like this i wish i had a chain back in my BSA days i always ran the engine breather to the chain! now i will have to think what needs lubing on the R1100

[Herb]

Hi Mark,

..... until your bike decides to dump 200ml of oil at the side of your back wheel.

Hmmm, I'm just wondering if anybody has ever found 200ml of oil in their airbox. I doubt it.

The quantity was a guess, and perhaps an overstatement. The point was, I would personally not want an oil breather exiting too close to my back wheel. Especially on a bike that is commonly overfilled with oil and known to drain oil (not mist) into the airbox. The originator of this thread seems to be comfortable with where he has positioned the drain.

I remember back in my youth it was commmon to see bikes with certain modifications, such as K+N pod filters running the drain into a collector, such as an old beer can or the like. Maybe you guys could fashion a collector from an appropriate German beer bottle in keeping with the bike's origins!

[el-nicko]

Personaly, I very much doubt BMW took the decision (probably prompted by some Californian emissions legistration) to vent the c/case breather into the airbox if there was any chance at all of large enough quantities of oil acumulating there to swamp the air filter. However, they would'nt have put a couple of small drain points at the bottom just for the fun of it and the 'gunk' that runs out when you open one is merely oil mist that has 'settled out'. It's interesting to note though that nowhere in any liturature have I found instructions relating to periodic draining of the airbox . As to overfilling; I think you would have to pour in some serious amounts of oil before it started gushing out of the breather, situated as it is, at almost the highest point possible on the c/case. I should imagine (and I'll stand correcting on this) that the problems of overfilling are more to do with oil reaching the height of seal lips and finding it's way past them into places it shouldnt get. I think the breather is only there to allow any build up of c/case air pressure/vacuum (caused by heat/piston blow-by/cooling?) to equalise to atmosphere. I myself have routed my breather down along the touque arm and am 'intensly relaxed' with the arrangment.

[Herb]

The pistons move in opposite directions, so bdc is on both pistons at the same time. Hence the potential to pressurise the crankcase is higher than in other engine configurations.

There are enough anecdotal reports of clean oil in the airbox in significant quantities to convince me it is a potential issue.

[el-nicko]

The pistons move in opposite directions, so bdc is on both pistons at the same time. Hence the potential to pressurise the crankcase is higher than in other engine configurations.

Yes, of course you're right Herb, I'll modify my post. And since I'm bald as a coot I can't even claim it as a 'Blonde Moment'.

[Mike B]

You don't need much oil to pump it into the filter box.

I drained my oil and refilled with exactly the right amount in the book. This actually overfills the engine. I found a substantial amount of oil in my airbox afterwards. It certainly was'nt from mist.

I looked into venting my breather outside the airbox but with the information I found on the internet, I decided to leave it "as is"

The reason it seems is that a breather into the airbox actually extracts fumes from the crankcase and helps to keep the oil clean. Apparantly this is one of the reasons service times have increased over the years. Engines are now much cleaner internally.

http://www.106rallye.co.uk/members/dyno ... ystems.pdf

[nab 301]

l.

.

Maybe you guys could fashion a collector from an appropriate German beer bottle in keeping with the bike's origins!

Not German but...............

[el-nicko]

http://www.106rallye.co.uk/members/dynofiend/breathersystems.pdf

Very informative Mike. Thanks for posting that.

[Dai wiskers]

Interesting indeed Mike now i'm not going to argue with you but would like to put over my theory [possibly very flawed but what the hell]

Here goes all the info on crankcase breathing i could find was on multi cylinder engine's mainly four cylinder car engine's now with a four cylinder you will have very little crankcase pressure take the oil cap off your car when it's running and you will see this is due to the fact that you have two pistons going up and two going down therefore ballencing each other out .
Now remove the oil filler cap on your bike as it's running you have just covered the left side of your bike with oil the reason for this [other than me wanting to have a laugh as your shiney bikes got oil all over them] is due to the fact that our bikes have two pistons both going in together and out together [if they moved one in one out the thing would vibrate like hell but we would have far less pressure] causing far higher pressure in the crankcases hence the noise and pressure when the oil is forced out of the oil filler
From what i can work out we have two breather systems fitted to our bikes one vents into the timing case [hence the oil leak that some of us suffer at the front of the engine] the oil leak can be reduced if you leave the bike on it's sidestand for a few minutes before putting it onto the centrestand just as you should do before checking your oil level, and one into the airbox [about time eh] the one were talking about i dont think there are any valves in this breather just a plate covering an appature that in turn is connected to the air box via a unrestricted [i think] tube that runs to the airbox, in all honesty i feel this has been done as i believe it's illegal in some[most] countries to vent to the atmosphere so this is an easy and cheap way out for the manufacturer.

All i know is the BBS in my bike get clarted up this cant be a good thing
The right one more so than the left now thats where the breather enters the airbox

Engine's running cleaner lets put that down to better filtration and oils

Please don't think i'm flaming or being argumentative i'm not [i'm sure you know thats not me by now]

Well thats my theory Dai

[Mike B]

I am on the fence, I can see the theory between both ways of doing it.

I guess the bottom line for me is. I just cant be bothered lol

I just get on with riding it .