07yz450 Question

4 replies to this topic
  • 00yzryder

Posted June 26, 2014 - 11:00 AM


So long story short the small plug used to see the timing marks fell out (yes it was in there tight no clue WTF happened and im pissed) due to where I was i had no choice but to run it home i did take it easy but i lost alot of oil. My oil filter had about a dimes worth of metal flakes in it. Im going to tear it down and probably replace the piston while im in there with a CP and see is anything else is damaged. My question is what else should i be looking for? Bike still fires up first kick every time, its lost alot of power thought which im hoping is the piston being destroyed.




  • grayracer513

Posted June 26, 2014 - 11:27 AM


If they are steel flakes (magnetic) and squarish in shape, that is an indication that there is a bearing falling apart somewhere. 

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  • 00yzryder

Posted June 26, 2014 - 02:56 PM


If they are steel flakes (magnetic) and squarish in shape, that is an indication that there is a bearing falling apart somewhere. 


ill check and see if they are magnetic at all when i get home. There was still a decent bit of oil in the bike but I know it only has a hair over a quart to start with so anything lost is a big deal... Hoping i dont need to replace anything else....


Thanks for you help.

  • 00yzryder

Posted June 27, 2014 - 09:24 AM


FML so the peices were magnetic, im going to drag the oil and see how much is in the oil (hoping not alot and the scotts trapped it all). Would it be the rod bearings that i need to take a look at or should it be pretty obvious?

  • grayracer513

Posted June 28, 2014 - 06:32 AM


There is a normal amount of iron in used oil from YZ that comes from the gearbox, but it won't be bright, uniform looking flakes.  Trans metal shed is long slivers at the biggest, and usually more like a fine black paste.


When a bearing starts spalling chips off the contact surfaces, it can be difficult to spot the source.  You have to really hunt for it sometimes.  Rod bearings that are going bad are really just about impossible to inspect, but most of them that are going bad will fail the measurements listed in the manual.

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