Cam bearing failures

5 replies to this topic
  • 2grimjim

Posted October 13, 2004 - 07:44 PM


I don't think this is a really big problem but it can be very expensive if it occures to you. I have a buddy who races a wr450 in the WORCS series that has had this problem twice since he's owned the bike (new). After the second incident I asked him if he was bleeding the air by loosening the small 8mm screw next to the banjo fitting on the cylinder head (I believe his reply was 'what screw?'). If you change your own oil in your yzf/wrf 250/400/426/450 the service manual explaines how to bleed air from the lubrication system after changing the oil filter. When you change the oil filter there will be air trapped inside the oil filter housing. If don't do this it takes a very long time for the air to be purged through the oil lines and passages. If you don't want to use the bleeder screw or crack the banjo bolt then lay the bike on its left side and fill the oil filter cavity with CLEAN oil before fitting the new filter and cover.

  • chipwich

Posted October 13, 2004 - 09:30 PM


REALLY good tip. Thanks! :cry:

  • Indy_WR450

Posted October 14, 2004 - 04:54 AM


I have never done it on my WR450. :cry: I have over 100 oil changes on my bike. Maybe my cam bearings are shot? :cry: I dont think so. :cry:

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  • ddialogue

Posted October 14, 2004 - 05:07 AM


I don't recall reading anything about purging air from the oil lines in the manual. I only remember reading about loosening the oil line on the back of the cylinder after an oil change to verify the oil is pumping. :cry:

I'm gonna read through the manual again.
4,700 miles on the old 03 WR450 and it's still going strong. :cry:

  • ncmountainman

Posted October 14, 2004 - 06:35 AM


i also believe its just to verify oil pressure,the oil will not move any faster through the line whether there is air in it or not. i'm pretty sure the oil drains all the way down every time it sits for a while,i have changed the oil filter without warming it up before and very little oil came out. :cry:

  • 2grimjim

Posted October 14, 2004 - 12:02 PM


You may not have a problem, however the owner of the bike that has had the problem was also using the cheapest oil known to man. Regardless of the ultimate cause the cam journals were damaged from lack of lubrication and the end result was a cylinder head being replaced twice. All that I'm saying is that given the right circumstances a problem could be created and I would choose to err on the side of caution. I have allways followed the service manual procedure for oil changes on my old '99 wr400 as well as my '03 wr450. I never have had to adjust the valves on either of these machines. If you have a cam bearing problem it will manifest itself as a zero valve clearance problem on the right and center intake valves. I beat the snot out of both of my wr's and they have proven to be exceptionally reliable machines.
The devil is in the details, my friend!


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