2003 WR450...another question

4 replies to this topic
  • dbeau626

Posted June 03, 2009 - 04:39 PM


Hello, I have also been having trouble with the check valve cover located at the top of the cylender coming off, and thus leaking oil onto the "header pipe," any clue whats going on here. The cap fell out once when I out too much oil in it and again when I didnt drain out the proper amount. Will ordering a new one and hence creating a tighter seal prevent this from happening?


  • DrBosa

Posted June 05, 2009 - 06:01 AM


If you are referring to the rubber plug on the front of the head, just above the exhaust, its not for checking valves, its supposed to plug the hole where the manual decomp mechanism sat on earlier models. This plug blows out if you get too high crank pressure, eg. when overfilling oil or accidentally squeeze the crank ventilation rubber hose between skid plate and frame (as I did once). There are several threads about this already, so do a search on "rubber plug" and you will get a few tips.

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  • bg10459

Posted June 06, 2009 - 05:16 AM


Check this thread -->http://www.thumperta...ompression plug
It looks like Zipty racing makes a decomp plug.

  • dbeau626

Posted June 07, 2009 - 06:39 PM


Good to know, I ordered another one, originally it came off because I overfilled it with oil, I drained alot of oil (down to about half) and it ran fine for a couple trips and then it fell off again while riding causing oil to spray on the exhaust, not sure what the explanation is for that, maybe the new one will fit tighter? any thoughts?
Thank you,


  • diegox450

Posted June 07, 2009 - 06:43 PM


Excessive crank pressure could be caused because of worn piston rings, that could be the cause


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