Engine Oil in Air Filter box

[revhappy]

Hello everybody,

 

I have a bajaj pulsar 180. Today I opened the air filter and was surprised to see oil in it.

Looks like engine oil has gotten into the air box. Anybody has experienced this before and can you let me know what could be the cause please?

 

[Raptor]

The crankcase breather vent goes to the air filter box to be recycled via the carb and combustion chamber to be burnt so as to reduce pollution.

 

Oil misting will occur in the air filter box if the piston rings are worn or the oil level is too high in the crankcase.

[crazydj]

Agreed. The engine oil from the crankcase travelled to the airbox via the crankcase breather hose. Its nothing to be alarmed about unless your air filter is drowning in engine oil.

[MiddleAgedBiker]

In most bikes there is a plug on the end of the crankcase breather hose. It's part of regular maintainance to drain the contents in the hose, but it is often neglected as bike shops typically will not do this for you. Give yours a check, if there is one.

[ezzyoiler]

if top overhaul..esp valve setting past due to do it...blow back is the result..

 

blow back power stroke gases going past inlet valve and blow past your carb and into air filter..

 

if your bike has gone through more than 60k km..lookout for this issue..loss of power is expected..

Edited February 24, 2011 by ezzyoiler

[MiddleAgedBiker]

I don't think that's how it works bro.

 

The blowby is the result of combustion gases (your fuel/air mixture) getting ignited and the pressure of the combustion forces these gases past the piston rings. Normally this is not supposed to happen when the rings are sealing well, but if they're not, these combustion gases gets pushed past the rings and start to pressurize the crankcase itself.

 

In the old days, the excess pressure in the crankcase will just find it's own escape route past oil seals or even past the gasket of the joined crankcase halves, which will lead to a bottom end oil leak.

 

Nowadays, because of environmental concerns, manufacturers have to route these blowby gasses from the crankcase back into the air-intake system so that it's burned in the combustion chamber. That is why you get engine oil in the filter. The oil comes from the vented gases mixing with the oil inside the crankcase.

 

The combustion mixture in your top-end above the pistons contain no oil (if you discount the oil on the surface of the cylinder wall).