Crankcase Breather

[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 .

[Dai wiskers]

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 .

I will admit i'm still unsure but will be trying it, if it seem,s to help i will keep it that way, if not i will reconnect it to the airbox

In all honesty it does seem to be the wrong place to have a breather i would have thought that venting to the exhaust would be better but think of the plumbing needed and you can see why that's not been done

Another thought that keeps rearing it's ugly head to me is the fact that if you pay a group of scientists enough they can prove without doubt almost anything to be fact [alcohol springs to mind is it good for you or bad with all the confusing infomation available good or bad? blowed if i know]

Oh to hell with it let's have another pint

[r550s]

FWIW I always had astonishing amounts of oil in the airbox, maybe not 200ml, but getting on for that much.
I thought I'd rather blow the oil mist into the atmosphere, so I rerouted the crankcase breather to a little K&N, fully expecting it to be sodden with oil after a while.
This never happened, It's been on a while now and all it ever has inside it is a faint whiff of oil.
Interesting point about forcibly extracting fumes from the crankcase though.

[South_Oz]

I wonder if having an Induct or not may make a difference. Without one fitted there might be a slight negative pressure in the air box because of the restriction in the standard inlet duct? Just a thought.

Dave