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You guys getting piston slap at partial throttle?

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I thought I was getting some knock at part throttle, but it has been brought to my attention that it may be piston slap instead..

'07 all oem parts.

When I am in a decent gear but just cruising (say when riding on a road for example) if I try to give it part throttle I hear knocking.. if I twist on it harder it tends to go away... or if I let off and then twist harder it goes away.

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I doubt anyone will say that's normal. Well, every high perf thumper makes a slight knocking sound if you put your ear up near the cylinder in neutral and change the revs a little. But your situation needs some investigation. Did you write elsewhere that you've clocked up 150 hrs on the stock top end?

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All I ever hear is chain slap, could that be it?

was about to say the same thing, what kind of a noise is it? i noticed you said "knock" but is it a chatter sort of noise by any chance?

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They do slap the piss out of the chain guard...

If you're certain in it's the motor, you sure it's not detonation?

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numroe.. no I am nowhere near 150 hours on the top-end.. I am probably half that. (wouldnt hurt to change it anyway).

Also.. the bike has did it since day one.. I attributed it to chain slap and didnt worry about it.

I made a post in the jetting forum and eddie sinsernos(sp) insisted that it was piston slap and completely normal.

evan1: it certainly is a chattering sound a rapid one.

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I get the same sound with my 07 when I'm way down in the RPM's lugging around at partial throttle. As soon as the RPMs come up it totally goes away. This is only when riding in gear. Bike is brand new with around 4 hrs on it. Does the chain normally only slap when lugging way down low a gear tall like when trying to ride quietly past a house?

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yah thats the same thing im getting.. I am pretty confident that it is just chain slap.. I checked by tightening the chain to a point thats really tighter than recommended specs, and the slap goes away. Now im not worried about it..

It had me fooled, it really did sound like detonation..

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You should worry if you run the chain tighter than it should be. Not a wise option.

A reasonable quality chain, with normal slack on aligned sprockets should make very little cracking noise at all. I'm not suggesting it to be over loose.

IMO what causes that loud chain cracking is lateral "flick" movement in the chain (not up/down), and occasional chain smacking into the left sub frame mount boss. Problem worse at certain revs and load, when you get that back-lash through the whole drive train.

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yah thats the same thing im getting.. I am pretty confident that it is just chain slap.. I checked by tightening the chain to a point thats really tighter than recommended specs, and the slap goes away. Now im not worried about it..

It had me fooled, it really did sound like detonation..

Cool... with this being my first 450f I didn't notice it until I was lugging way down low trying to be quiet past some homes until I can get a Q4 silencer and it does in fact sound just like detonation.

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I didnt leave the chain tight like that, I just tried it out for 5 minutes to see if it was making the sound and sure enough it was... now I have it back to about 2" of slack and it makes the sound again..

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glad to hear this, my 07 also does this and it had a rebuilt right before I bought it. When lugging it before the rpm's really pick up I get a rapid fire clicking sound like a machine gun firing in rapid succession but its out of bullets, click click click click click?

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glad to hear this, my 07 also does this and it had a rebuilt right before I bought it. When lugging it before the rpm's really pick up I get a rapid fire clicking sound like a machine gun firing in rapid succession but its out of bullets, click click click click click?

Yup, that's it.

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damn and I was trying to think of a good way to describe it too and now he comes along after we got it figured out.

thats definately the sound, and its definately the chain up front. Just FYI it does sound a whole lot like detonation, so if you ever hear that coming from your car or your bike, and you know its the engine not the chain, u have a tuning issue.

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What's happening is the engine is bogging due to such low RPM, causing the jerk in the drive train, jerking the chain and making the slapping noise. It's the same as coasting to 5mph in 3rd gear in a 5spd car and then giving it gas, the car is going to chug along until it gets up to a good rpm.

Almost any bike will make that noise when chugging along at slow speeds or low rpm.

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Right.. the thing is, these bikes are doing it at like 5k rpms which you would think is high enuff RPMS but its not.

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Right.. the thing is, these bikes are doing it at like 5k rpms which you would think is high enuff RPMS but its not.

I was going off of you saying you were cruising at part throttle. Do you have a computer with a tach on your bike?

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nah i just know where the bike idles and basic idea of where it happens in the power band.

I will happen in 5th gear, even when im crusing at 40 mph or so (again a guess) the motor isn't lugging, it revs fairly freely. It seems like its more to deal with the tension put on the chain.. when u twist harder its pulling on the chain harder and no slap... when ur light throttle cruising it rattles around..

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nah i just know where the bike idles and basic idea of where it happens in the power band.

I will happen in 5th gear, even when im crusing at 40 mph or so (again a guess) the motor isn't lugging, it revs fairly freely. It seems like its more to deal with the tension put on the chain.. when u twist harder its pulling on the chain harder and no slap... when ur light throttle cruising it rattles around..

Got ya. I was assuming the conversation was about at low rpm travel. But you're right, not much tension will lead to a little slappage of the chain.:thumbsup:

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my 06 made that sound and had a cracked wrist pin. You should probably take a look before it gets catastrophic. I heard the noise in the beginng of a moto and just rode it out, which was dumb, but it held together, and would get quieter when pinned....I wallowed the upper connecting rod hole a little but it never did fail.

the 07 ran for hundreds of hours and never had a problem though.

All of my KX's. especially the 450's slap the crap out of the chains if you are in a partial throttle situation.

I doubt its the wrist pin, but man gaskets are pretty cheap.

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