Excessive Oil from breather line

7 replies to this topic
  • tgodwin

Posted January 24, 2005 - 04:23 PM


Have a 99 WR400, just bought it, been on three rides with it. I checked the oil prior to the first ride and it was full. Before I went on the third ride (yesturday) I checked the oil and it did not register on the dipstick. I've laid the bike down twice in the two rides nothing hard, and got it right back up no obvious leaks or spills. I was told buy the previous owner that oil does spit out the head breather tube occasionally. I saw a couple small oil puddles under the tube outlet in my garage and thought nothing of it.

After yesturdays experience I belive a lot of oil is making it into and thru the breather tube while riding. I had a nice fresh oil coating on everything down that side of the bike at the end of the ride. I'm watching the oil consumption closely. It is not burning oil, no blue smoke; no smoke for that matter and runs excellent.

How much is too much oil to be loosing? I've read here that possibly the valve seats need to be replaced, correct? Anything I missed?

Thanks in advance. :cry: :cry: - Tim

  • duckboy

Posted January 24, 2005 - 06:31 PM


Valve seats wouldn't cause that, but valve seals for the exaust valve stems could. Most like the cause is gases blowing by the piston rings which means getting the cylinder honed and a new piston.

  • jchantzWR400F

Posted January 24, 2005 - 06:34 PM


I can't comment on the valve seats but I can tell you that the oil loss you describe doesn't occur with my 99 (neither here nor there). My advice would be to make sure you always check the oil level after the bike has warmed up for at least 3-5 minutes. My oil never registers on the stick before that time frame.

  • yamaha-er

Posted January 24, 2005 - 07:52 PM


I agree with the previous post. Start your bike and let it warm up a little before checking the oil level. I own a 01 WR426 and there has always been a little dribble of oil coming from the breather tube since new. It has never been enough to ever effect the oil level.

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  • WheelsUp

Posted January 24, 2005 - 07:59 PM


Ya... there's a reason the manual says to warm it up, then let it sit for 5 minutes before checking.

These are dry-sump systems. When running, the frame reservoir will be full.
After sitting overnight, you will read nothing on the dipstick, as it will all drain down into the case.
Yamaha has set the dipstick length to show a correct reading when the engine has been shut off for that specific length of time. Check it any sooner and it's going to read high. Check it when the engine is cold and it'll read low.

Some people go absolutely nuts trying to get the level absolutely perfect after an oil change. I just dump in 1.5qts and make sure that it's ON the dipstick. If it's too high, being dry-sump, it's not that big of a deal. There will be a little more windage on initial startup, but once it's pumped into the frame it's fine.

  • tgodwin

Posted January 24, 2005 - 09:58 PM


Thanks for the feed back. I'll check it correctly from now on. I knew the bike had to be warm, but maybe I didn't warm it up enough. I'm just going to keep an eye on it for the next few rides.

I incorrectly said valve seats, I meant seals. If they fail what kind of symptoms would indicate a problem?

  • WheelsUp

Posted January 24, 2005 - 10:04 PM


Leaking valve seals will cause you to burn oil.

For excess oil from the breather line I would suspect PERHAPS excessive crankcase pressure due to weak rings (how's your compression?), but overfilling can also result in excess oil from the breather.

Like I said above, when stopped, the oil will eventually bleed down into the case. I am not 100% certain of the capacity of the case itself, but I strongly suspect that is IS sufficient to hold 100% of the oil in the system.

If that is the case, then an overfill could cause excess oil to be thrown into the top end by the timing chain at startup, which could find it's way into the breather tube.
I remember one guy saying that he had overfilled his YZ and he just had some extra oil coming out of the breather for a few rides.

  • tgodwin

Posted January 24, 2005 - 10:12 PM


Thanks Rich. It's not burning oil and runs great. I haven't done a compression test, but the guy I bought the bike from said he put new rings on it less than 100 miles ago. He pampered this bike. I think I'm just a paranoid rookie.


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