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rickallen124

Motor noise

5 posts in this topic

I just got a 08 YZ450 the other day and noticed that the motor makes alot of noise compared to the YZ250f that I have. I also noticed that when you disengage the clutch the noise stops. I imagine this is normal, but I don't remember my friends 06 making this much noise. I can't wait to get this thing broken in and on the track.

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Normal thing for the YZ/WR450. My '03 WR450 and "06 YZ450 are noisy and have been since day one. This is an issue Yamaha has been dealing with for the last few years. The noise you are hearing is from the clearance between the clutch plates and the basket/hub. When you pull in the clutch lever it allows the plates to 'float' and they no longer bounce around in unison. Another source of noise is from the primary and balancer gears. Yamaha has been tightening up the tolerances on these parts in the last few years to deal with this.

Way back when, manufacturers would sometimes use 'helical cut gears' to reduce primary gear noise but with some unwanted side effects. Although helical cut gears are stronger and quieter than straight cut or 'spur gears' they impart axial thrust loads on the mainshaft and crankchaft and contribute to heat build up and excessive bearing load.

The noises you are hearing have absolutely no influence on the reliability of your machine.

[edit] The reason it is more noticable in the 450 is the difference in size and mass of the intermal components is considerably more than the 250.

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I just got a 08 YZ450 the other day and noticed that the motor makes alot of noise compared to the YZ250f that I have. I also noticed that when you disengage the clutch the noise stops. I imagine this is normal, but I don't remember my friends 06 making this much noise. I can't wait to get this thing broken in and on the track.

Once again:

http://www.thumpertalk.com/forum/showthread.php?p=5362282#post5362282

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