Air Filter Sludge

[Quarteg]

Hey everyone, it's been a long time.

I ran the built-in search engine for the site as well as this particular forum for my 1986 GL Aspencade and came up empty. I changed the air filter yesterday and I noticed there was a yellow gelatinous substance around the ring of the filter.

Also, underneath the filter was grimy... not slimy but very dirty.

Truth be told, I have no remembrance of the last time the filter was changed.

I figured since I was replacing my back tire and brake pads (front and back), I would change my spark plugs and air filter. (oil was changed last month or the month before) The spark plugs were black (oil, not burnt) so I am hoping everything is fine with that now.

So the question is, do I need to worry about the sludge? There was not a lot of it, maybe two or three tips of a large flat head screw driver.

I'm attaching a pic of the plugs, the dirty filter, and under where the filter sits. I never thought to take a pic of the air filter sludge.

Thanks in advance.

[WingAdmin]

When the engine runs, some of the compression gases in the cylinders make it past the piston rings, this is called blow-by. These gases get into the crankcase, where they mix with oil. The gases contain all the usual byproducts of gasoline combustion, including a lot of water vapor.

You can't pressurize the crankcase with these gases, as you'll end up blowing out seals. So there is a ventilation hose (called the crankcase ventilation) that allows the gases to escape. These gases are highly noxious and polluting, so you can't just vent them to the atmosphere, instead there is a hose that leads from the crankcase to the bottom of the air filter box, where the gases get sucked into the carburetors and burned again.

These gases contains both water vapor and oil mist. When they hit the relatively cool environment of the air box, the water vapor can condense, where it mixes with the oil mist and creates a sludgy emulsion. This is the goo that you are seeing in there.

Incidentally, this is one of the main reasons it's not a good idea to run your engine periodically during the winter to "exercise it." The oil in the crankcase doesn't get hot enough to boil off that water vapor, and instead that (now highly acidic) water condenses and sits in your engine, where it corrodes everything it touches. At the same time, the water vapor in the exhaust collects in the exhaust (which also doesn't get hot enough) and corrodes it as well, from the inside.

[Quarteg]

Thank you so much. I will stop my panicking then. lol

Is it possible for the hose from the crankcase to become clogged or slightly restricted like a heart valve? Should I even bother looking at the hose to make sure I am getting the most air flow? Or is this something that once I start running the bike everything will be fine?

As far as winter running, I always tell my friends not to do it. I think it was you that suggested it a while back, to not just turn the bike on and run it for a short time in winter as it can cause damage. That said however, the only time my bike runs during the winter is when the salt is off the roads and I decide I want to ride.

[WingAdmin]

Thank you so much. I will stop my panicking then. lol

Is it possible for the hose from the crankcase to become clogged or slightly restricted like a heart valve? Should I even bother looking at the hose to make sure I am getting the most air flow? Or is this something that once I start running the bike everything will be fine?

As far as winter running, I always tell my friends not to do it. I think it was you that suggested it a while back, to not just turn the bike on and run it for a short time in winter as it can cause damage. That said however, the only time my bike runs during the winter is when the salt is off the roads and I decide I want to ride.

That hose is pressurized, so it won't usually become clogged. It could possibly come off the air box (usually forgotten during air box reinstallation) in which case you'll notice gooey sludge dripping all over the engine and floor.

[Quarteg]

Sounds good.

Thank you again for your help.