2007 yz450f problem

4 replies to this topic
  • case77

Posted July 28, 2010 - 11:30 AM


i got this bike not to long ago and it doesnt have many hours on it. i rode it the first time and the oil blow by tube was blowing out a lot of oil. This can be 2 things, the oil was not over filled it was at the correct amount, and i went ahead and installed OEM rings. The piston was stock and was in almost new condition. I rode it after installing them the next day. There is still an abnormal amount of oil coming out of the blow by tube, not as much as the first time i rode it. But the problem now is the little hole on the right side of the cylinder ( i think its the weipe hole for the spark plug is leaking fluid, after a day of moto's alot of fluid has came out of it. I check the coolant and oil after each time i did a moto and there both full. somebody please help ???

  • outcast623

Posted July 28, 2010 - 11:32 AM


could it be the valve cover leaking instead on the breather tube? and it is also leaking into the spark plug hole?

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Posted July 28, 2010 - 12:10 PM


that hole on the side of the cylinder is for anyhting that gets down the sp hole. VC gasket sounds blown.

  • gdbarr1976

Posted July 28, 2010 - 01:11 PM


My guess is you have a bad cylinder/piston. The piston/cylinder/rings is not keeping the compression in the top of the cylinder. It's blowing by into the bottom end and forcing oil up into the valve train area and the only place it has to go then is out the vent hose. I'm guessing new cyclinder. Sorry, but only a guess.

  • case77

Posted August 02, 2010 - 05:40 PM


The piston is in good shape, the sleeve had just small scratches nothing to the point where it would need to be re sleeved, so i just took a honing tool to a electric drill and swiped it in there a few times, but i installed new rings just in case

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