I've got a 1991 FLHS. Recently I have noticed a LOT of oil leaking out of the air box. It mists the fairing that covers the oil tank. When I get home from a ride the fairing covering the oil bag will have a coating of oil on it and oil will drip out of the bottom of the air box and onto the motor. It doesn't leak oil when it is sitting, just when it is running and just from the air box. It seems to be pushing oil out of one of the vent tubes that vent into the air box. Has anyone else had this problem?

Is it a blow by problem? Is one of my cylinder sleeves or piston rings letting oil through or something? It isn't burning an oil and is very strange to me. I can't figure it out.

 

Could be an excess of blow by gasses indeed. Whats the mileage of the engine? Has anything been done recently to the bike that might have caused this? Done any maintenance or repairs lately?

I had a similar problem (https://www.hdforums.com/forum/evo-c...-cylinder.html) a while back caused by broken compression rings. You might want to do a compression test in order to be able to rule things out.

 

Your 91 would not be a 'top breather' so that would rule out issues with that. Unless later model heads were installed and plumbed into the air cleaner backing plate. Has the cam chest been open? If the breather is out of time, or is FUBAR, it could possibly cause an issue like this.

Did you change the engine oil recently? How much did you add?

What air cleaner are you running? OEM? Aftermarket?

 

Start with a leak dwn test with someone that knows how, or at least a Compression test.
Next, - like Hacked said -should be non-breather
But
These parts get homogenized by people that do not know the difference.

 

If it just started doing it...my first guess is just running too much oil in the tank.

Most people remove the vent tube from the air filter, and route it toward the ground to prevent the mess...and they make fancy little filters to keep critters from getting in your vent hose.

 

First thing I would check is the oil level. Make sure you check it hot right after at least a 15 minute ride. I was checking mine cold and adding too much oil. I was also getting a lot of dripping at the air filter.


carl

 

They all do it somewhat. Still do. Especially if you run it at the upper rpm range and let it sit for a few days letting oil that got dragged along with the vent gas from the pressure created when the piston was on the intake stroke. (The piston puts pressure in the crankcase and that air needs to go somewhere) Wipe the drool from the old girl's chin and keep getting up. It's been perfectly fine for 27 years and will be for another just like it is.

 

The bike has about 12k miles on it. No major work has been done to the bike recently. Did an oil change recently thinking this might be the problem. Filled to spec. Eventually the oil light came on because the bike had leaked so much oil through the air filter. Bike still leaked oil even when low on oil. I will look into a compression test.

I have not opened the cam chest. I did change the oil recently I do not recall how much oil I put in exactly but I'm pretty sure it was right around 4 qts.

How can I look to see if mine is a stock "non breather" or if it has been changed?

I'm fairly certain it doesnt have to do with oil levels since it will do it up until and after the oil light has come on. I add some oil the light goes off and it continues to leak oil the whole time at the same rate.

Its a lot more oil than a little drool.

 

OK, did not realize it was leaking that much...if you have that much oil coming out of the breather ....the breather gear and bore are probably toast.

 

The mount bolts for air filter are hollow all the way into the head.