Leaking Breather Cover

[J_C]

My engine (as acquired from the PO) is coated with think black grime. It appears to be the result of a leaking breather cover (I assume as such being that its the highest piece and it's also the filtiest. Upon removal of the cover the gasket appeared to have bubbles, and there was a little bit of oil seeping through the screw in the middle of the breather assembly.

Is it feasible for oil to leak through this gasket? And if so, is the gasket the source of the problem, or is there something else that has led to the bubbling of the gasket? Should there be that much oil floating around in there?

[tfb]

The 'bubbled' look to the gasket just means that it's OLD, and has put up with years of engine vapours and heat. It's not essential to get a new one, I think, but since you've got it apart you might as well indulge.

Oil can leak through any gasket with enough time. If the breather area is particularly oily, that could be because you have excessive 'blow by' past the pistons, and the blast of gas escaping past the piston rings is carrying oil vapour from the crankcase upwards into the breather area. In which case, it's time to freshen up or overhaul the top end (piston rings, etc.).

Question: is oil appearing in your airbox? ie. making its way down the tube from the breather cover into the airbox? If so, that will indicate excessive blow-by, also.

Mike.

[Road_Clam]

My engine (as acquired from the PO) is coated with think black grime. It appears to be the result of a leaking breather cover (I assume as such being that its the highest piece and it's also the filtiest. Upon removal of the cover the gasket appeared to have bubbles, and there was a little bit of oil seeping through the screw in the middle of the breather assembly.

Is it feasible for oil to leak through this gasket? And if so, is the gasket the source of the problem, or is there something else that has led to the bubbling of the gasket? Should there be that much oil floating around in there?

It almost sounds like to me you have excessive oil vapor passing through the system. Did the hose that connects the breather to your airbox have excessive oil in it? If it did, this indicates excessive piston ring "blowby" (meaning tired rings). Vaccume from the airbox removes normal pressure from the crankcase so as to not harm the rubber engine seals. The rectangular steel mesh filter is supposed to trap oil, and prevent further passage into the hose and airbox. Clean everything up, and drive your bike and keep an eye on the airbox. If you see raw oil in your airbox, you have a blowby issue.

[J_C]

Thanks guys. I never noticed any oil in the airbox... but come to think of it the hose may not have even been connected to the airbox when I bought it. That might explain why there was so much oil down on top of the crankcase as well. I have purchased a new gasket and its on the way. I will check the hose for oil when I get home. I may have to run it and be watchful like roadclam said.

God help me if I start messing around with pistons

[sf-nathan]

Definetly attach that hose from the breather to the airbox.

The airbox vacume should pull air out of the engine and keep negative presure on the engine.

Also the airbox should have that hose as the hole for it is post airfilter (if I remember correctly. It will suck in dirt without that hose.

Cars have this. On my '86 volvo its called the 'Positive Crankcase Ventilation', and helps with engine presure blowing seals.

[J_C]

Thanks Nathan, I'll give it a look!