Valve Cover gasket keeps blowing

Yamaha WR450F 2007 Electrical Electrical Components Trail Tech DC Converted Stator Kit

29 replies to this topic
  • pbcrazy9898

Posted July 20, 2016 - 03:39 AM


Yes it is possible to install it like this.  I've got parts on order right now.  Im crossing my fingers hoping this was the reason the gasket was blowing. 

  • GuyGraham

Posted July 20, 2016 - 08:12 AM


Well if it was always the exhaust half moon that was popping out then its a strong possibility its this

  • pbcrazy9898

Posted July 20, 2016 - 10:10 AM


One time both half moons blew. The other two times it was just the exhaust one. Could that rubbing cause a spark or enough heat to cause an explosion?

  • GuyGraham

Posted July 20, 2016 - 11:02 AM


I highly doubt it

  • WRfinatic

Posted July 20, 2016 - 02:59 PM


Is there another spot on the valve cover to hook up a pressure gauge? Last time I had myne apart I seem to remember another rubber hose just in front of the crank breather hose, that would be a great place to hook up a pressure guage to tell if its pressure blowing it out or not



_Nevermind  I see you already started the bike with the breather disconnected, I should have read that first!

Edited by OldRM, July 20, 2016 - 03:02 PM.

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  • pbcrazy9898

Posted July 29, 2016 - 05:27 AM


I thought I'd update this thread to show the end results of my repair efforts.  Hopefully this thread will help someone else out in the future. 

I think I finally figured out the root of my problem.  The camshaft sliding out has been fixed even though I believe now it was unrelated.  Thanks to a TT member, fengluzon, he recommended I checked the stator.  Apparently when a stator starts to fail it can arch and cause the fumes inside the crank case to ignite and blow the valve cover gasket.  I guess it happens on sport bikes more often than dirtbikes.  I thought this was pretty crazy but I was out of options and wanted to get to the bottom of this issue.  I pulled the case off and found some definite evidence of arching and lots of little metal shavings.  My light has been very dim lately and my battery wasn't charging either so this all is starting to make sense. 

Anyways I installed a trail tech 100w stator and the bike runs stronger and the lights are all much brighter.  I haven't ridden the bike long enough to confirm the gasket blowing problem has been extinguished but I'm pretty confident this is the fix.

I will post an update in a while when I know it is fixed.


edit: uploaded one more pic

Attached Thumbnails

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Edited by pbcrazy9898, July 29, 2016 - 05:29 AM.

  • JoeRC51

Posted July 29, 2016 - 12:49 PM


I'm sure a stator could arc , but there aren't enough fuel fumes in a crankcase to ignite. Enough fumes to ignite would have your oil so diluted by fuel to cause major friction damage in a motor. Also arcing would'nt make metal shavings at all , you'd have burn marks and possibly slag , like from welding.

  • pbcrazy9898

Posted July 30, 2016 - 08:41 AM


I just went for an hour ride yesterday and so far the gasket has not blown and Im about to go for another ride right now.

There are certainly flammable fumes in a crank case that can ignite - not necessarily from fuel.  (google it)  Also this is the thread that gace me the idea to check my stator.>  http://www.bcsportbi...p/t-122169.html


PS The metal shavings probably came from the auto decomp gouging my cylinder head.  (see pics in some of my earlier replies to this thread)

  • WRfinatic

Posted July 30, 2016 - 08:29 PM


With the right conditions anything will ignite. Also remember as the piston goes up it draws fumes from the air box into the crankcase thru the breather tube. Would have never thought a stator would cause that, great thread!

At least the valve cover gasket blew instead of a engine seal leaving you stranded or seized

  • pbcrazy9898

Posted August 04, 2016 - 07:50 AM


I thought I'd wrap this thread up:

Rode the bike for a good 5 hours this weekend and the valve cover did not blow.  Soo I'm knocking on wood as a write this,  but I think I fixed it. Problem Solved

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