04 YZ450F connecting rod seize

3 replies to this topic
  • project yz

Posted August 28, 2015 - 03:57 PM


I recently picked up a 04 YZ450f that has a seized con rod. The crank can still move but the con rod wont rotate. I'm wondering what could have caused this I've been thinking oil starvation was the problem and want to redo the bottom end right and make sure it is completely clean of dirt/debris. 


My question is what should i really look for to replace and how can I flush the oil system in the frame of dirt/debris because i found one of the oil lines coming from the engine to the frame to be damaged and had alot of dirt around it. Is there a way I could dump some diesel through the frame oil system to clean it out?


any insight is greatly appreciated, I'm a bit new to the Yamaha 4 strokes 

  • project yz

Posted August 28, 2015 - 04:01 PM


Also what tools are necessary for taking the bottom end apart? I ordered a flywheel puller and clutch holder tool. Could I do it without air tools? My air compressor is not big enough to run a air gun.

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  • grayracer513

Posted August 29, 2015 - 08:11 AM


It's a lot more fun with an air impact, but I don't use one for too many things out side of the clutch boss and output shaft.  


Download a manual from the two links near the bottom of the second post in the Common Threads pinned topic.  


You can maneuver around most of the special tools needed to replace the crank, although the crank installer might become necessary.  The usual cause of rod bearing seizure in '03 and early '04 YZ450's is a failed rod bearing roller cage.  The bearing wears, the cage cracks, and the rollers skew out of line and jam the rod.  If they skid too much when that happens, they seize. 


While you're doing the engine, look over the oil pump, and be sure to replace the oil seal in the right crankcase cover that slips over the end of the crank.  Note the way the seal is installed before removing it. 

  • project yz

Posted September 03, 2015 - 02:44 PM


I've ran into a problem... the stator torx bolts are extremely tight and I can't get them loose no matter what I've tried, also tried easy out on them and just made more of a mess.il. Is there some trick somebody knows to get them loose?

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