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Coolant Leak In Head/Cylinder

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Hey everyone!  I'm riding a 2005 YZ450F with an Athena big bore kit and FMF Q4 can.  

 

I've been riding this bike just about every weekend for the last month, still getting a feel for it and getting it dialed in.  Since I started riding it 4 weeks ago, I've noticed some coolant loss that I originally associated to bad rad cap.  I replaced it with a 1.6 bar Helix cap, and didn't lose hardly any coolant 2 weekends ago.  Sunday I was out riding Jewell MX track and was really pushing the bike hard.  At the end of the day (about 2.5 hours of seat time) there was a noticeable amount of coolant dripping from under the motor.   Upon further inspection, I discovered that there is a small metal pipe with a right angle that appears to have a bad O ring or seal.  It also appears to have a coolant hose attached to it that may run to the radiator.  Didn't seem like the water pump was leaking, as I thought it was that at first.

 

Has anyone had this problem before?  Is the O ring/seal only available from the dealer, or can I use a generic O ring?  Thanks!

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You can use a common O-ring IF you can find the correct size, both in outside diameter and the gauge of the ring cross section.  The dealer will (should) have one, though.  The same seal is used in several locations on a number of different models. 

The pipe is the water outlet from the head to the left upper radiator tank.  Clean the pipe in and around the O-ring groove with Scotch Brite, steel wool, w.e., as well as the socket in the head that it plugs into. Slick up the O-ring with just enough grease to leave a film on it and slip it back together. 

 

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On 4/25/2017 at 11:46 AM, grayracer513 said:

You can use a common O-ring IF you can find the correct size, both in outside diameter and the gauge of the ring cross section.  The dealer will (should) have one, though.  The same seal is used in several locations on a number of different models. 

The pipe is the water outlet from the head to the left upper radiator tank.  Clean the pipe in and around the O-ring groove with Scotch Brite, steel wool, w.e., as well as the socket in the head that it plugs into. Slick up the O-ring with just enough grease to leave a film on it and slip it back together. 

 

Do you happen to have the measurements for that O ring?  Haven't had a chance to dis-assemble yet and was hoping to pick one up before I do the job.  Don't feel like paying $5 from the dealer when I know I can get them for a $1.

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i would just pay the $5 and be done with it because then if you put it back together and it still leaks you at least know that it was the right size part and not off by just a hair. it isn't like spending an extra $4 on a machine like that is going to break anyone.. then you know it's right..

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Well, that was an easy fix.  Snowed today and was super slow so clocked out a little early to knock it out.  Old O ring was completely flat.  Wasn't much crust on it, but I took the entire outlet pipe to the wire wheel and cleaned up nice.  A little pitted on the hose end, but nothing major.  Decided to flush the entire system while I had it apart and upgraded to Engine Ice.  Rinsed it off and fired her up.  Had to come about 1.5 turns out on the fuel screw to comp for the 30* air.  Did some wheelies around the lot and no more leaks.

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