Slight knock/ vibrations when idling YZ450F

dereck519
Maybe this has been brought up before? Maybe this is in my head but I noticed today when I started my bike that my engine gets a bit louder (almost a slight knocking sound) and a little more vibrating in the handlebars when idling for a second or two, then goes away, then a few seconds later comes back then goes away and continues like this until I rev the engine, When the engine is revved there is no vibrations or any odd sounds. I rode it for a 20 minute moto with no problems, but do not want to continue this if this is a sign of bad things to come, or is this normal? The vibrations are not rattling the whole bike, I can just notice it a little in the bars when I am holding them. The bike is a 2014 YZ450F. There are no other signs of engine issues such as smoke or loss of power. I do have a Recluse EXP 3.0 clutch installed aswell, but no other modifications to the engine.
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Paw Paw
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Benton, LA US
Paw Paw 9/13/2016 6:22pm
9/13/2016 6:22pm
The Recluse can give off that sound.

Paw Paw
dereck519 9/14/2016 4:38pm
9/14/2016 4:38pm
Thanks, that makes sense. Revving the engine would tighten the clutch up, thought this could be a possibility.
1stSSPZ
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1stSSPZ 9/16/2016 5:32am
9/16/2016 5:32am
My 13 did the same thing after mounting a Recluse. I have had 5 different YZ450's and they all rattled somewhat. Never had a failure on any of them including a 99 YZ400 that must have 300hrs, at least!
dereck519 9/20/2016 2:09pm
9/20/2016 2:09pm
Wasn't the Recluse, took it out and still had the same sound. Then tore the cylinder apart and noticed a score up the front side, and thought that the piston was a little sloppy, so I honed the cylinder and replaced the piston with one from before that was still good (replaced after 45 hours), and still had the noise. So, today I tear it completely down and noticed that it appears the crank was spinning inside the crank bearings (wore through the coating on both the bearings and crank. Not a speck of dirt or metal inside the motor. Shocked this happened as 1stSSPZ said, I have seen these bikes go literally hundreds of hours before needing a crank. Well, Rocky Mountain is gonna be loving me right now as I put this order together. Smile

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Zycki11
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Zycki11 9/20/2016 3:20pm
9/20/2016 3:20pm
dereck519 wrote:
Wasn't the Recluse, took it out and still had the same sound. Then tore the cylinder apart and noticed a score up the front side, and...
Wasn't the Recluse, took it out and still had the same sound. Then tore the cylinder apart and noticed a score up the front side, and thought that the piston was a little sloppy, so I honed the cylinder and replaced the piston with one from before that was still good (replaced after 45 hours), and still had the noise. So, today I tear it completely down and noticed that it appears the crank was spinning inside the crank bearings (wore through the coating on both the bearings and crank. Not a speck of dirt or metal inside the motor. Shocked this happened as 1stSSPZ said, I have seen these bikes go literally hundreds of hours before needing a crank. Well, Rocky Mountain is gonna be loving me right now as I put this order together. Smile
Good on you.... Saved yourself from a possible disaster and major cost.

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