Oil pools in the air box

[Einar]

Hi everyone,

I took off the air filter today, and discovered that the box below was full of oil (engine oil, i presume).

1. Where might this oil come from?
2. What is the function of the T-section tube? Ventilation system from the crankcase?
3. The engine oil level is exactly in the middle between min/max on the fuel gauge stick. Could it be that it's still too much?

When I removed the carburaters, I saw oil pools inside the cylinders as well, I was advised the ventilation system might dispose oil into the airtube. Is this what I also see in the airbox?

4. If so it would mean that the black tube behind the airbox is the vent-tube from the engine, yes? Am I then right to assume that the seal between the black tube "behind" the box and the T-section must be poor and that's how the oil gets in?

This oil leaks down on the outside of the engine (from under the airbox, appears to come out via the hole that bolts the box to the engine), and creates a mess on the external parts, preventing me from clearly evaluating the integrity of other seals such as driveshaft.

5. Do I need to change the oil filter? Milage unknown.

Any help would be greatly appreciated.

[Bob_Roller]

It's pretty common to get oil in the airbaox and have it drip out of the carbs .

You may want to check the crankcase breather valve to make sure it's still working, or even installed, if you are not the original owner, previous onwers can do some weird things to their bikes .

On '81 model year bikes and later, it's just a metal reed valve, on the earlier bikes, it's a spring loaded valve .

A usual cure, is to not fill the oil to the full mark, some bikes just atomize the excess down to a point, then the level stabilizes .

What weight oil are you using

[Einar]

Thank you for your reply Bob_Roller.

Great tip. I will look for the crankcase breather valve. I was not even aware of its existence. Where is the valve situated?

I am not the original owner, it's an R65, 1981.

I just bought the bike recently, I've been told by the previous owner the oil is Castrol 10w-40 synthetic. I am planning to change it.

[montmil]

Remove the top cover just forward of the air box and you'll spot the breather valve. There is also a small drain hole nearby that provides a return to the sump. It must be open. Probe with a pipe cleaner.

[Semper Gumby]

Normal.  Lived with it for years.  There is a rubber reed valve on the back of the air box - some may drain out there.  Wouldn't worry about it too much.  Helps lubricate the top end.

[Einar]

When you say "top cover" you mean the engine cover under the gas tank that is bolted to the block? That sounds like quite a job, I will try to get on it this weekend.

At least it is good to know it is nothing pressing and I can drive it without causing any serious damage.

Thanks guys and have a good weekend.

[montmil]

When you say "top cover" you mean the engine cover under the gas tank that is bolted to the block? That sounds like quite a job, I will try to get on it this weekend.

You can see the cover in your photos. Sits just forward of the upper part of the air cleaner box. If memory serves, there are but two Allen-head screws that hold the cover in place.

[Einar]

Update on the air box story:

Over the weekend I opened up and got to the breather valve.

It seemed like the reed valve was installed and functioning (I can bend it, I assume that means it's working), however;
1. The tube from the breather valve and connection to the t-section seemed to have come loose - possible leak source
2. The gasket under the breather valve housing was probably from 1981 (along with most of the important seals on this bike) - possible leak source

Questions:
a. Does anyone have the part number for the gasket under the breather valve?
b. Part of a clamped down housing just in front of the air box is cracked and partially damaged. What is this piece and is it a concern that it's damaged?
c. Can anyone point out the drain valve from the photos attached?
d. Any other possible leak sources that you can see from the pictures?

Will open up again in a week's time after having driven around a bit to see if the oil has disappeared + install breather valve gasket.

Thank you all for your help!

[Bob_Roller]

This should show you all the parts you need .


http://www.realoem.com/bmw/enUS/showparts?id=0364-USA-09-1980-248-BMW-R65&diagId=11_1712


Just an added note, I saw a ' modification ' to the crankcase breather about 22 years ago,  a simple job, cut a piece of a copper pot scrub pad and place it in the housing of the breather valve, not enough to clog the airflow, but just enough to let the atomized oil collect on the pad and then get returned to the sump .

Seems to work, I get very little oil in the airbox, or oil dripping out of the carbs since I have done this .

[Einar]

Excellent! Thanks for the link and modification advise.
Your input is invaluable.

[montmil]

As to your 'drain hole' question, look just forward of the crankcase vent flapper. There is an area referred to by BMW as a settling chamber. At the bottom is a small drain that returns oil to the sump... unless it's clogged up. Pipe cleaner, small wire, whatever but confirm to opening is clear. The drain is on Airheads mfg'd from 1978 onward.

The photo is from an engine cutaway lifted from The Snowbum's website. Thank you, Robert Fleischer.

[Einar]

Thank you Monte, great input! Yeah that hole looks like it could clog up easily.

[Barry]

As to your 'drain hole' question, look just forward of the crankcase vent flapper. There is an area referred to by BMW as a settling chamber. At the bottom is a small drain that returns oil to the sump... unless it's clogged up. Pipe cleaner, small wire, whatever but confirm to opening is clear. The drain is on Airheads mfg'd from 1978 onward.

The photo is from an engine cutaway lifted from The Snowbum's website. Thank you, Robert Fleischer.

Anyone actually seen this hole on an R65 as opposed to other airheads ?
Don't know about the later models but my 79 doesn't have it.

[nhmaf]

The tips the guys gave you are all good - another thing to also consider since I couldn't see it in your pictures - are the hoses/tubes that are supposed to go out of the airbox from the T-connector down to the vacuum ports on the carbs in good shape and not blocked up?   These may need periodic replacement due to age/cracking or getting plugged up with a combination of oil and road dust.

[Einar]

Good point! I will verify that there are no obstructions on the hoses from the t-connection.

1 Question:
Could a bad air filter cause this?

I ordered air filter + Gasket for the breather valve, once it has arrived I will open the bike up again to change parts,change engine oil (10W-40) and verify integrity.