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Oil coming out of air box

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A friend of mine. Has a 2006 crf450. He changed the oil. Then went out riding and oil started coming out of the air box. He thought he might have put the oil filter in backwards. He checked it and he found that there was metal in with the oil and filter. He rebuilt his engine top and bottom end about 30 hours ago. It just seems strange this happened after an oil change that it started doing this. Anyone have any ideas.

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Possibly to much oil? I had a 04 250f that was pulling oil from the trans side into the motor side and sending the excess out the exhaust and air box.

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Quite possible he blew a head gasket and coolant is mixing with the oil and coming out the overflow into the airbox.  That's exactly what happened to mine recently.

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may be he doesn't drain the engine vent tube,   or may be he spent some time on the ground with the bike laying down

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On my Polaris 4 wheeler this was happening dealer said it was suction from a bad air ox design you would ride it and it would be half full of oil

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I jumped on the forums tonight for this very reason. I have an 07 CRF450r that recently had oil coming out of the air box. I too recently did an oil change(like I've done many times). I was at the track last saturday when i first notice it but figured I haven't drained the crank case vent tube in awhile. Today I noticed it again so I drained it again and went for another moto and it filled again. After researching I have come to the conclusion that either balancer seal or crank seal is bad or its time for a top end rebuild. Do my conclusions seem right?

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I jumped on the forums tonight for this very reason. I have an 07 CRF450r that recently had oil coming out of the air box. I too recently did an oil change(like I've done many times). I was at the track last saturday when i first notice it but figured I haven't drained the crank case vent tube in awhile. Today I noticed it again so I drained it again and went for another moto and it filled again. After researching I have come to the conclusion that either balancer seal or crank seal is bad or its time for a top end rebuild. Do my conclusions seem right?

Too much tranny fluid possibly as well

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Too much tranny fluid possibly as well

I was thinking that too but I pulled the fluid level screw and I had to lean the bike over to get fluid to come out. Also last Saturday one of my buddies said my engine oil level looked low.

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If the gasket between the oil and tranny case blew then wouldn't his clutch slip? Also if his transmission fluid is over filled would the transmission fluid be coming out of the vent. Because he uses the red oil and that's not what was coming out of the vent

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