Oil dribbling out of the crankcase hose

I picked up a 2010 YZ250 recently, with extremely low hours on it. I've ridden it once last week and did not notice any problems.


Today, I took it for a five minute ride in a field to warm it up, then let it idle to tune the air screw.  I elevated the idle a bit and began to adjust the air screw. I was just about finished when I noticed a steady dribble of oil running out of the black case hose (just below the carb on the left side of the bike).


The bike was not doing this when I first began, but only toward the end, so I'm assuming it happened as the bike was getting hotter. I would not say the bike was overly hot as I was only riding for about 5 minutes, and then making adjustments for maybe another 5 minutes. The oil was only warm to the touch, not hot. 


I have never seen this before, but I had planned to change the oil after the bike cooled a bit. I don't know if the other owner has too much oil in it (I'll measure it when I change it) or if something else is going on...


Any ideas?

Edited by Clip67

How do you now it has only low hours?


And when there is too much oil in the crankcase hose let is out. Or you have a higher pression in the crankcase. 

Sounds like previous owner over filled the trans. Drain the trans fluid and refill with the correct amount.

Thanks guys - much appreciated!


I just drained the oil and measured it. I got 33 ounces (plus I spilled a bit) out of it. It looks like the P.O. put a full liter of oil in it (33.8oz). The manual calls for .75 of a liter or about 25.35 oz according to my math, so it looks like he over filled it.


Arnego2: The P.O. claims only 10-12 hours on the bike. I didn't know him personally before the sale, but he is a local over 50 vet rider. The local shop owner knows him well and confirmed the lowish hours on the bike. He has 2 other 450s and they are all well kept. It's hard to tell the hours exactly as there was no hour meter, and he had an aftermarket chain and tires on it. Sprockets looked pretty good though.


I'll have to post a pic as the bike is pretty cherry. For $3k, I couldn't pass it up!

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