2014 rmz450

I recently replaced a crank in a 2014 RMZ450 because the crank rod bearing went out. The guy that brought it to me said it was leaking oil from the vent tube the day it "locked up". The guy has rode the bike twice since I put the crank in. The first time everything was fine no oil coming from vent tube. The second time he rode it oil came out of the vent tube. He didn't change the oil in between rides. Question is why would it happen one time and not the next? Also what caused the rod bearing to go out so soon on a 450? Thanks in advance.

Too much oil or blown head gasket, sounds like your pressuring the crankcase, also could be crank case seal put on backwards

Too much oil or blown head gasket, sounds like your pressuring the crankcase, also could be crank case seal put on backwards

How would I be pressuring the crankcase?

Too much oil, blown head gasket or a crank seal put in backwards.........

I know the seals are installed correct and the head gasket should be fine because it's new and it leaked oil before I replaced the gasket. That leaves me with having to much oil. If it had to much oil why would it come out the second time it was rode and not the first time.

Just because the head gasket is new and was in good condition when you installed it or that it wasn't blown the first ride does not mean that it is not blown now. I've seen them blow within seconds of starting the bike after a brand new one is installed. If I was a betting man and you said it did not lose oil on the first ride, I would put my money on the head gasket (assuming that your crank seals are in fact installed correctly.)


What Rotaholic is saying is that one of those things is very likely your issue... that does not mean that you caused it, but things happen. There are a handful of reasons that a head gasket could blow. If you are confident that your crank seal is not installed backwards then one of the other two options is more than likely the problem. 

Edited by BDubb106

Thanks! I believe the seals are put in correct. Of the top of your head do you know which side of the seal goes out on the right crank case? I have an extra set of seals and will replace it if I've done it wrong.

Flat side towards the bearing. Lip faces out. 

Okay that's the way I installed them. So I'm gonna replace the head gasket. But I'm gonna ride it again because I drained the oil and the guy had changed the oil. When I drained it 1200ml came out. Gonna make sure it's not just overfilled before replacing the gasket

1200 is fine, how much coolant is there? Is it using water? head gasket normally fail by the cam chain sending pressure straight to the crankcase

It's not using coolant.

A dead giveaway is a ticking noise coming from the head for a blown gasket.

I would do an oil change, tear the paper filter apart and check the metal strainer, check for anything odd, check the oil, is it milky, shinny smell burnt etc do a fresh oil filter and oil change and ride it again and see how it goes.


Would pressuring the cases cause the crank to go out like it did? I'm just trying to find an answer to why it would go out. If not just because of time.

Also Would a bad cylinder or piston cause pressure to leak by the piston into the cases?

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