breather question...

Hi people, excuse me for my poor english. I want to ask you something - On the upper crankcase cover there is placed the cover of the breather (where the gases from the crankcase are being cleaned from the oil mist)...what must be there under the cover ? Are there any parts that clean that gas ? Maybe a some kind of filter ? I'm asking cause under the breather's cover i found only an empty chamber...is that OK ?
And my second question is what to the breather hose must be attached ? It must end in the air filter housing, right ? (I have the European version, without the air suction valves).
Thank you in advance for your help.
Svilen, Bulgaria

Post edited by: scorpio, at: 2006/10/02 16:50

My kz1000 ltd has the same setup but has k&n air filters. I put a long piece of hose over it and zip-tied it up under the seat to the chassis... I don't have a filter on it. My bike does not "blow-by" so it's ok.

And there are no parts under the cover of the breather ? I thought that there must be something that is lost...
and somewhere i read that this gas from the crankcase after being cleaned from the oil mist in the breather, must be reused by the engine through the carburettors...so it must go to the air filter housing...Is this right ? And is it mandatory ? Or it is enough the gas to go to the atmosphere (not reused by the engine) for crankcase ventilation just like in floridamba's bike ?
I forgot to tell you that the bike is Kawasaki GPZ750.

Post edited by: scorpio, at: 2006/10/03 02:35

It depends on where you live, how strict your air pollution laws and what year your motorcycle is. My LTD is an 1982 and it had a vacuum-activated air injection into the exhaust valve area. I took it off as it was broken and did not function.

I have a small air filter to put on the breather hose but have not found the right size adapter yet for it. I used a piece of auto heater hose to connect to the breather on the crankcase, then routed it up and under the seat, using a zip tie to hold it under the seat.

My engine does not blow any smoke out the hose so it's not having any blow-by gases. If yours does this then you may get some oil mist coming out the hose. I would put a rag over it to screen it out or use an air filter for it, they cost maybe $10.

The purpose of the crankcase breather is to provide ventilation. There is no filtering under the round cover. If you remove it, there will be a round metal plate with a couple short hoses but the purpose is to allow air from the crankcase to excape so that pressure doesn't build in the crankcase. The only time anything actually will come out the opening (with air) is oil and that oil is the result of the piston rings allowing excessive oil past them... this is caused blow-by and can be caused by cylinder ovaling, bad rings or chunks missing out of the pistons. There is little reason to put a filter over this vent. The only real problem would be an insect crawling down the hole. Most bikes will blow a small amount of oil mist out of the hole especially when the oil is real hot or slightly over-filled so putting a hose on the vent is a good idea and routing the hose back over the swingarm keeps any residue off the engine. If you have SOME blow-by and operate the bike, the hose is a necessity as you will have a mess in the area otherwise.

Thank you for the answers people.
wiredgeorge, that "round metal plate with a couple short hoses" is the thing that i have no under my cover Maybe it is not very important part, but anyway...it will be cool if somebody can show me a pic of that thing - from the net or elsewhere...i tried to find it in one microfiche, but it is not shown there

I pulled this from the parts diagrams for a KZ900 on buykawasaki.com under Crankcase/Breather.

OK...thanks for the pic...