400f Oil preasure

I just changed the timing chain on my 98 YZ400F. Now it is blowing oil from around the dip stick cap. I changed the o-ring with now luck. The hotter the engine gets the more it blows oil. Some oil also drips from the radiator, but I don't know if it is coming from the fill hole or not. It seems to have way to much oil pressure. Any help as to where to begin looking please????


YZ400f #09

Could be the water pump seals. Check it out!

Just an idea , but could your screen be plugged?


If I remember correctly there is a vent hose which goes from the top of the oil resevoir to the top of the valve cover. Make sure this isn't pinched or plugged up.

Some things seem to simple to ask...but. Did you set the oil level after running the bike (hot) or before(cold)? You have to run it before checking the level or you will overfill it (dry sump engine). That may and probablly is to basic for someone who has the ability to chenge the timing chain, just a thought though.

Is the plastic on your dipstick cracked? I would also make sure the oil line on the left side of the frame that runs from just below the dipstick to the motor is tight.

Good luck and let us know what you find.


Originally posted by npuzajr:

Just an idea , but could your screen be plugged?


That was going to be my next step, but I feel that if the screen was clogged the oil would not make it to the pump and therefor not to the fill tube. I'll let ya know what I find when I check the screen. Thanks

Originally posted by YZ400Court:

Never to simple to ask. Most times I ask myself how can one miss something this simple, but it does happen and we feel like an idot. I changed the oil at the same time as the chain. I put 1.9 quarts or whatever the book said, then ran 5 minutes and checked. Still thinking maybe I miss messured or something I drained 1.5 quarts out. I guess .3 blow out of the fill tube.

[This message has been edited by YZ_Maniac (edited October 22, 2001).]

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