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2009 YZ450F piston knocking?


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I have had the 2009 YZ450F for about 1 year and have put maybe 25 hours on it. I have not raced the bike or even rode it extremely hard. I change the oil and clean the air filter after every other ride. Just this spring I noticed a hollow sound coming from the motor when it is is idle or low rev. It almost sounds like I can hear a gentle knock in there and I am wondering if anyone else has this problem or if they would know what it is???

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my 09 YZ450F has 14hrs on it. and it too has the same "hallow" sound (at idle). but when i pull the clutch in, the sound is non existant. i'm thinking harmonic noises from the clutch plates and basket is the cause. i beleive my previous yamaha's did the same thing and i think it's normal.

the previous bikes have never had clutch failures or any other issues

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Thanks for all of the comments back concerning the noise. I sure am glad this is a normal sound, it just seemed like I didn't hear this noise right off of factory floor. After adding the skid-plate I could definately hear the nose alot clearer. I will continue to ride without putting too much worry on the sound. Thanks again

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Thanks for all of the comments back concerning the noise. I sure am glad this is a normal sound, it just seemed like I didn't hear this noise right off of factory floor. After adding the skid-plate I could definately hear the nose alot clearer. I will continue to ride without putting too much worry on the sound. Thanks again

WIth the skid plate added it sounds like they left some jap engineers in there with ball peen hammers! They all do it! Your fine!

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That's nothing to do with the piston. Read:

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

yeah, i know the clutch (plates and basket) has nothing to do with the "piston", i never said it did.

i was merely stating that when the clutch lever is pulled in and the clutch is disengaged, the noise (hollow sound) isnt present.

thanks for the link you (grayracer) provided. it was educational. but i still think the clutch is the culprit of the noise

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I have an 06 yz450f that does that... I didnt know what it was at first, but i scared the crap out of me! and its pretty liud, but like original ad said you pull the clutch in, it stops pretty fast, or if i go any more than 1/4 throttle it disapears too. I thought i bought myself a lemon for a minute there untill i read this. thanks for the post!

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