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2000 400exb
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Discussion Starter · #1 ·
I recent did a full rebuild on top and bottom end, everything’s great except for the fact it pukes oil out the crank breather into the airbox. Ive doubled, triple checked oil is not overfilled or underfilled… anyone else have this issue after a full rebuild?
 

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I've seen it happen if there was no gasket installed between the case halves - the gasket creates a baffle to keep oil out of the breather - if the gasket was installed and since the engine is a dry sump, either the return side of the oil pump is not returning all the oil to the oil tank and the engine is wet sumping or perhaps the oil lines from the tank to the engine are reversed and the pump is pushing against the check valve in the oil tank fitting - or the check valve was left out of the engine or the oring seal between the clutch cover and the oil pump was left out?
 

· Registered
2000 400exb
Joined
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3 Posts
Discussion Starter · #3 ·
I've seen it happen if there was no gasket installed between the case halves - the gasket creates a baffle to keep oil out of the breather - if the gasket was installed and since the engine is a dry sump, either the return side of the oil pump is not returning all the oil to the oil tank and the engine is wet sumping or perhaps the oil lines from the tank to the engine are reversed and the pump is pushing against the check valve in the oil tank fitting - or the check valve was left out of the engine or the oring seal between the clutch cover and the oil pump was left out?
Ok thanks! I cant remember where the check valve location, was it was over a year ago since i rebuilt it, do you know?
 

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OK - I was wrong, it's not a check valve, but a pressure relief valve build into the oil pump and that would not be the problem as it is on the high pressure side of the pump. I will now guess that you have a clogged oil screen, a faulty o-ring between the oil pump and the clutch cover or a faulty oil pump.
 
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