Oil Passage Question 03 YZ450

5 replies to this topic
  • stepside

Posted April 18, 2008 - 07:15 PM


I had the right crankcase cover off of my 2003 yz450f on the weekend while changing water pump seals and I noticed what looks to be a damaged seal.

The seal in question is located on top of #25 in the diagram below. (the Oil passage with the check ball going to the oil filter) What has me really stumped is that it is not shown in this drawing and I couldn't find any info in the manual regarding this seal. At first glance it looked like an O-ring but it appears to be kinda pressed in there with the slug (#25).

Is it part of #25?
Is it just residual assembly glue of some kind and not a seal at all?
What am i seeing here?

Thanks for the help


  • stepside

Posted April 19, 2008 - 03:32 AM


Thanks for the response grayracer

I think i see what you mean only there is no dowel on the upper port of the oil pump or crankcase cover. The lower port of the oil pump going to the exterior feed line does have a dowel and o ring.

The seal is almost partially pressed into the journal where the slug #25 is and i cant get it out and that is why i am confused. I have #5 there but that is the lower port on the oil pump and this seal is on the upper port/passage to the oil filter.

Thanks for the help

  • grayracer513

Posted April 19, 2008 - 05:05 AM


The dowel sleeve (#6) is critical. It's what keeps the O-ring in place. Get a new one when you replace the seal.

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  • stepside

Posted April 19, 2008 - 01:09 PM


I have #6 and the o ring, the passage that i am having problems with is on upper port on the oil pump (shown directly right of the number 7 shown on the drawing in post #2) which meshes with #25 shown in post 1. The check ball and sleeve is pressed into the right side crankcase cover and is flush with the surface.

The seal appears to be pressed in there with the sleeve which is what has me stumped on how to change it and what part i need to order.

  • grayracer513

Posted April 20, 2008 - 11:56 AM


The ball seat, #25 in the first post, has an "O-ring" built into it. If that seal is damaged, the seat should be pried out of place and a new one installed. The O-ring and dowel I mentioned first are not directly associated with the oil pump itself (my bad) :thumbsup:

  • stepside

Posted April 20, 2008 - 02:40 PM


Thats exactly what i need to know, ill be ordering the seat right away

Is there anything i can do besides a simple oil pressure test to check that everything has gone back together correctly after the install.

Thanks again for getting me on my way greyracer, the season is just a little to short up here to be scratching my head for too long.:thumbsup:

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