2010 yz450f siezed

3 replies to this topic
  • RagingBunny

Posted July 18, 2014 - 10:31 PM


Here's the story, 

I bought the bike yesterday, was super excited to ride it so I just went straight to a local riding spot (something I usually never do after buying a used bike). Once there I checked over everything, and everything looked good. Coolant levels were good, oil levels were good, it looked ready to ride. But here comes the fun part... After letting it fully warm up, went for a quick ride around to make sure it ran fine. It had a tendency to stall a lot but I was expecting that because it was still in full MX setup and I hadn't set it up for hare scramble racing yet. After the warm up I hit the trails. I got in about half a kilometer where I got to a very technical section. Of course the bike stalls and I get stuck and was forced to turn back to the bottom of the section and take the easy route...  :smirk:  So I start it up and ride to the bottom were I stall again, and I go to start it again. Except this time the kick starter wouldn't budge. It was fully seized. I tried rolling it back and fourth in gear, bump starting, everything, it just wouldn't un-seize. It would still shift fine, I just couldn't move the kick starter at all. After many curse words, yelling, kicking and screaming, I got back to the truck and went home. :censored:  So today I started to tear it apart, still had full coolant and oil. After doing some investigating I decided to check the timing. I removed the cam chain tension-er and I hear a huge clunk. It was un-seized! :applause:  So what I'm assuming is that the cam chain skipped a tooth on the camshafts and seized the engine. Can a cam chain get worn to the point where it will skip a tooth? Also what kind of damage am I looking at? I stalled and it seized while I was idling so hopefully nothing to costly  :banghead:. I also noticed that the chain was a bit loose when under tension then normal. (I owned a 2008 yz450f) 


Here's a pic of the Intake and Exhaust camshaft teeth.



  • grayracer513

Posted July 19, 2014 - 07:19 AM


The problem is likely the chain itself.  The way the usually fail is by having links tighten up and bind instead of pivoting smoothly.  Replace the chain and the tensioner.

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  • RagingBunny

Posted July 19, 2014 - 11:00 AM


Thanks for the reply, I'll order new parts today, hopefully that's all the damage that happened!

  • raptorgabe

Posted July 30, 2014 - 11:41 PM


ive seen this to 3 different bikes and usually its the chain skips timing and the piston smashes valves

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