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Oil coming out vent hose?

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My '04 RMZ was idling in the garage the other day, and a 4-5" pool of oil came out of the transmission/crank vent hose. It was very weird. I was idling the bike to warm it up and change the oil. Has anyone seen their bike spew this much oil? I'm wondering if it was just a freak thing, or is something clogged?

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This exact same thing happened to my neighbor on Saturday. He had just bought it brand new and brought it home. He started it up to warm it up so we could take a couple hot laps and all of a sudden it started puking oil too. He was all freaked out and I tried to calm him down but he rushed it back to the dealer and they couldn't explain it. They said to ride it and that it had a 30 day warranty and let them know if there were any more problems.

I told him that it was excessive crankcase pressure because the rings have yet to seat and the bike is a 'wet sump' design with a lot of oil in the crankcase. I explained that to him and told him we need to go riding Sunday and ride the sh*t out of it to seat the rings and the problem should go away. Needless to say he was freaked out all day but we rode 30 miles and the bike ran great.

I guess the bikes just don't like to idle long. 😢

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The crankcase was most likely overfilled and the oil you saw was the excess. Check the level of the oil now, if it is within the lines then you have no problem, if the oil is below the line than there is something more serious going on and I would not recommend riding the bike until it is fixed.

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It wasn't an oil level issue, because the oil was actually low (on the low side of the window line). I saw some posts on this about a year ago, but didn't sound like anybody figured out what it was. The bike is only about a month old to me (bought from someone else), so not sure if this has happened before.

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Don't use the oil sight window. It's very deseptive. Mine did the same thing. Once I drained everything and used a ratio rite to put in the exact amount, there were no more issues. I lot of people including dealers, will add oil to the middle of the site window and overfill them.

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The problem most people experience is that they tip the bike to one side or the other and they get a false reading. There is such a small amount of oil that even a few degrees is the difference between a low reading and a high reading. I still don't consider the ratio rite method fully accurate because you never drain all the oil, it is certainly very good but not perfect.

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This has happened at least one time to everybody on here, not uncommon, next time it does it pull the vent hose up higher on the carb rev it a couple times 1/4 throttle usually takes care of it, the sight glass half full is a very accurate measurement, thats why its there, in winter or colder months be sure to use a lighter viscosity oil, the venting system on this bike is through the idler gear, as it spins it vents air sort of like a vacuume {so to speak} just make sure if it is spewing oil you get it to stop, the only time I have ever seen one doing it is at cold idle start up,

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That is the culprit, the oil is clinging to the gears effectively climbing to the top where the idler gear is. As art5 pointed out, the gearbox is vented through a series of orfices and chanels made into gear itself and its supporting shaft. the shaft itself is the same part the breather tube is connected to on the outside of the engine, it is basically hallow. As long as the oil level fine, do not worry about it.

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