Oil coming out of air box...what could be the cause???

I just got a 1981 Yamaha XJ 550.

I rode it home and had no issues and then rode it for about 20 miles (120 km/h or less). After this, my riding buddy noticed oil on my back tire. It was coming out of the air cleaner. There was quite a bit of oil but it quit dripping after a few hours.

I looked at the manual and it looks like there is an air cleaner breather hose coming from around the oil pan/filter/crank case. Some people have said this might be blow by but I am not sure.

What may cause this problem and what can I do to fix it and then prevent it in the future. I am kind of worried it might be a more serious problem.

 

Too Much Oil?
It'd probably take the path of least resistance... rather than blow-by your rings (GASP!) it'd get pushed through the PCV. I have a Seca 400 and had chocolate milk for oil when I bought the bike. This was caused by water getting into the intake while it sat for 7 years, and draining into the crankcase via the PCV hose.
I'd change your oil/fitler, pay attention to how much drains out... and what color, condition, etc etc etc!

 

Yes! too much oil in the engine! do a oil change... My bike did the same when I (bought it) brought it home, there was 5+ quarts of oil in her! (instead of 3quarts).

 

Check for Fuel in the crankcase. You might have leaking petcock and a float or two stuck...

 

Along with testing for too much oil ... you should do a Compression Test.

The Compression Test will tell you the story.
IF you have a Cylinder with Compression so low that you are getting Blow-By into the Crankcase ... you have to take corrective measures
BEFORE you have a Major Break-down.

Compression offers resistance to the Piston rising to a Point where it reverses direction and descends.
The Compression guarantees the Piston DOES reverse direction.
Without Compression ... the Piston will apply force on the Rod and Bearings to let it keep going ... straight out the top of the Engine ... without descending as it should.

The unchecked force results in:
Spinning a Connecting Rod Bearing ...
or
The Connecting Rod breaking ... letting the Piston go free.

Do a Compression Check
Consider yourself at risk until you KNOW the Compression Values to be within specs.

 

The PO of one of mine had a full gallon in it; no petcock or float problems, pure 100% oil-- all 4 quarts.

Common assumption, I've even seen it posted here in the same situation: Oil comes in a gallon jug, it must take the whole gallon. "All those old jap bikes take 4 quarts" NOT.

Breather hose on the 550 comes off the top of the clutch housing on the right side, just behind the number plate, and goes to the airbox.

The 550 takes (officially) 2200cc's of oil; put in about 2300-2400, the slight overfill is ok and keeps the oil level sensor happy.

On the right side, down low under the brake lever on the bottom of the clutch housing is a sight glass with two lines cast next to it. Ideal oil level is above the top line with just a bubble showing and the bike on the centerstand. With the bike on the sidestand, NO oil should be showing in the window.