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08yz450frider

Frame Concerns on New to me 08' 450F

12 posts in this topic

I just purchased this 2008 yz450f a few weeks ago.Its my first time on a bike in about 5 years. I took it to the local track and found something concerning when I was cleaning it after the ride.

It looks like the chain has chewed into the left inner frame rail.. The chain is adjusted to spec so I am not sure what has caused this... I am a pretty big guy who cases jumps on occasion..

Will this frame hold up over the next 3-5 years? Is this common at all?

The bike is SWEEEETTT otherwise. Previous owner said it had 20-25 hrs on it and it looks and rides the part..

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That's very common, in fact I'd bet if you look at most bikes at the track you'll see similar wear on a lot of them. Usually if there's too much slack in the chain it'll slap and hit the frame.

It won't affect the integrity of the frame at all, keep the chain adjusted properly from now on and ride that thing !!

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It's not a major concern, but DON'T tighten the chain beyond the minimum specified 1.9" under any circumstance. Read:

http://www.thumpertalk.com/forum/showthread.php?p=8906182#post8906182

One thing that will make your chain hit the frame (or the mud flap) excessively is a combination of a worn chain and and out of alignment rear wheel. Be sure you don't make the somewhat common mistake of counting marks on the axle blocks from front to back. The left side has a flange on the front edge to keep the axle from rotating when it's tightened or loosened, and that "covers up" one mark. Read them from back to front. Double check the alignment for accuracy the first time or two before trusting the marks entirely.

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Be sure you don't make the somewhat common mistake of counting marks on the axle blocks from front to back. The left side has a flange on the front edge to keep the axle from rotating when it's tightened or loosened, and that "covers up" one mark. Read them from back to front. Double check the alignment for accuracy the first time or two before trusting the marks entirely.

This is good advice! I counted the marks on the axle blocks to initially line mine up after replacing the chain, and noticed right away that it was horribly out of alignment. I ended up using a micrometer to align the rear wheels and completely ignored the marks on the axle blocks.

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Thanks. My concern was centered around the aluminum being a softer metal than the steel frame of older models.

I planned on dumping some money into this bike to make it a great machine, but didnt want to waste the money if the backbone( frame) wouldnt hold up...

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My buddy bought an 06' that had frame wear like this. It was a bit worse on his bike i believe. I made a thread on here about it for him and got alot of response that said it was not big deal. Check it out.. He still didnt like it and ended up selling the bike to someone who didnt think it was a big deal.

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The same thing happened on my 2007, it was a work in progress since I bought the bike with 30 hours on it. It got a lot worse than that up to the bikes demise at 150 hours. I didn't like it at all. When I bought my 2010, I didn't want the same thing happening. After one ride on the stock chain and seeing some scrapes, I made an aluminum guard that bolts to the chain roller inside the frame. It has complete swingarm clearance, and it works awesome. I can see the nicks in the guard, but my frame is no worse than what the stocker did on the first ride.

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The same thing happened on my 2007, it was a work in progress since I bought the bike with 30 hours on it. It got a lot worse than that up to the bikes demise at 150 hours. I didn't like it at all. When I bought my 2010, I didn't want the same thing happening. After one ride on the stock chain and seeing some scrapes, I made an aluminum guard that bolts to the chain roller inside the frame. It has complete swingarm clearance, and it works awesome. I can see the nicks in the guard, but my frame is no worse than what the stocker did on the first ride.

What was the bikes demise? Frame or motor? Also, can you describe your aluminum gaurd a little better? I would be interested in making one of these. Thanks.

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I bought mine the same way. Must be a pretty common. I haven't noticed any more wear now that I have it; but I may try making a cover like the guy above.^^^

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i always adjust the chain i have found 2 fingers slack just right a slack of 2 inches might do that but anyways its always repairable

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i always adjust the chain i have found 2 fingers slack just right a slack of 2 inches might do that but anyways its always repairable
Brilliant.

I have fairly large hands, and at the first knuckle, my index and middle fingers together measure 1.57" Yours may be two, I don't know.

But if you think it doesn't matter, try this:

  • Adjust the chain to 1.5" above the slider bolt
  • Remove the pivot bolt for the shock relay arm from the swing arm
  • Try to swing the rear wheel through its full travel.

The chain will be too short to allow it to do so without bending something.

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After reading this thread I had a look at my subframe and I have only a very slight amount of chain marks, and nothing like in the pic above. I wonder if when you run a cheap, and stretched roller chain and cornering hard LH, causes the chain to droop and contact the subframe ? I've always run a premium o-ring chain and possibly you don't get as much "droop" when the bike is layed over hard to the left ? Just some thoughts....

Chain contacting the subframe is also a big issue on my KX500, here's how we solve the issue before sawing through a $300 KX500 subframe. You might be able to perform a similar mod to the YZ's inner subframe :

http://www.kxriders.com/forums/index.php/topic,2492.0.html

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