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frgsn27

Yz450f 08 Cam chain problem

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My buddy and I both purchased 08 Yz450F’s at the beginning of the summer. After four rides (not including the break in), It felt like the there was an excess amount of compression when trying to kick them over, I never got it started. After taking it to the shop I found the timing chain tensioner failed, jumped time, and bent the valves on both bikes within a few hours of each other. Yamaha and Beaverton Honda the dealership we purchased them from said sorry out of warranty. Kind of a crappy deal considering they had less then 30 hours on them. In addition the bikes were maintained meticously in between those four rides. Has anyone else had this problem?

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i also had a 08 450 w/ about the same amount of hours on it jump time and totally wiped out every thing from the base gasket up.yamaha also told me the same thing so i had to fork out $1900.00 my self.got to love it!!!!

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Just happend to me last weekend. Thank god there was an engine on e bay for the same price it would have costed me to replace. I have an 02 426 that still runs like a raped ape and never had any problems. Maybe we can all put something together something for Yamaha. Kinda like a *** letter.

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I also have a 2008 Yz450 and just finished up with the chain last week.

Bike has 77 hours on it without any problems.

I hear the stator screws also come loose but mine were all tight.

It is the elect. part inside the left side of the bike outer case.

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There are about 5 cases including me I have read about with 08's that have jumped time and wiped the engine out. I read about one guy that had it all covered by Yamaha , so why not everyone with the some problems at the same amount of hours?

Man that 2G's really takes a bite out of the fun and the peice of mind / reliability I have had riding Yamaha's over the years. This bike had a little over 20 hours on it. I know it was running ritch.... m_3ed8ccc7b9b54b6590438c4dd7e1cd49.jpg

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Do you still have your 450 or did you sell it? As soon as i get this settled im selling mine. From what i have heard that inlet tube at the bottom has native pressure and sucks up dirt, doesn't sound like a good design for a DIRT BIKE.

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I also have a 2008 Yz450 and just finished up with the chain last week.

Bike has 77 hours on it without any problems.

I hear the stator screws also come loose but mine were all tight.

It is the elect. part inside the left side of the bike outer case.

How difficult of a job is it to change the chain? Thanks:thumbsup:

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This really sucks to hear. Hopefully yamaha will do something about it. In the 4 stroke era that we are currently in, Yamaha is said to be the most reliable and the one bike that you can have a peace of mind with, when i hear a failure like this from the "number 1 in reliability", it really is disturbing.

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A friend of mine had his bike do the same thing. Top end got pretty much destroyed. Thank god it is winter and I am soon going to over-haul my top end anyways.

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Do you still have your 450 or did you sell it? As soon as i get this settled im selling mine. From what i have heard that inlet tube at the bottom has native pressure and sucks up dirt, doesn't sound like a good design for a DIRT BIKE.

you mean the breather hose?

well, you heard wrong. it can only suck something up on the first cycle of a kick when the motor is off. once running, it pulls in as much air as the displacement of the cylinder and then pushes that same amount back out. basically, the same column of air moves back and forth very quickly, but never does it actually suck dirt into the motor.

putting your hand very close to the inlet would tell you this. however, instead you chose to listen to those without much intelligence.

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you mean the breather hose?

well, you heard wrong. it can only suck something up on the first cycle of a kick when the motor is off. once running, it pulls in as much air as the displacement of the cylinder and then pushes that same amount back out. basically, the same column of air moves back and forth very quickly, but never does it actually suck dirt into the motor.

putting your hand very close to the inlet would tell you this. however, instead you chose to listen to those without much intelligence.

It absolutely will suck dirt up into the motor. It did it on my '06 and on my '08 I never gave it a chance by putting a filter on it.

You can quote theory and mechanical design all day long saying that it can't but I have witnessed it happen.

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Dirt intrusion through the breather is a conditional hazard, and while it is possible, it depends on 2 things:

  • The bottom end of breather must be in contact with/below the surface of a source of sand, dirt, water, etc.
  • The engine must be turning at a speed below an idle, i.e., coming to a stop, as in a stall out, or while being started.

In operation, the pressure reversion takes place too quickly to either draw in or expel a volume of air larger than that within the hose, so the engine will not ingest foreign material through the breather while it runs.

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