08 450 headshake

Hey guys my buddy just got a leftover 08 yz450 on a trade for his 09 kx250. Anyway, he has been havin terrible problems with headshake on high speed straights. The bike is stock havent really done anything to it as of yet. What could be some of the causes/cures for this problem.

Front, or less likely, rear tires not seated on the wheel bead correctly, low tire pressure, or a bent rim can lead to this. Absent any of those things, the rear wheel misaligned in the swing arm can also cause it. Head shake can be a bit difficult to pin down a cause for.

Read:

http://en.wikipedia.org/wiki/Speed_wobble

I have an 07 YZ450F and mine did the same thing. I sped up the rebound on the forks and that did the trick for me...

if no mechanical issues then check tire pressure, set sag correctly, adjust height of forks in triple clamps and check clickers. I had this as well when I bought my bike. I run forks 5mm up in clamps, comp and rebound 2 clicks each softer than stock. I also have sag at 96mm on my 07. Shock at MXA clicker settings for comp and rebound. These bikes are very sensitive to setup. How much does he weigh? Stock springs are for someone around 160 to 180 lbs. With these changes my bike turns very well and is stable now with no headshake. Less sag really helped to increase the stability. Run bars more forward too if needed. These bike are known for stability, its got to be in the setup if nothing is broken or bent.

Hope this helps

thanks alot guys were gonna try your suggestions tomorrow at the track. he is 180 so springs are prolly good the tire was misaligned a little bit. the weird thing is that he just got like 5 hours ago, i guess the dealer just threw it together or something.

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