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2007 crf450r knocking sound


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So at idle I am hearing a knocking sound (jack hammer sound).

Video:

http://www.youtube.com/watch?v=XQmG3Tpe3Wc (I am slowly rolling the throttle a bit in the video to give you an idea of how the sound changes at different RPM).

The bike starts on first kick, even when hot. It idles low without a problem and never misses.

Here is what I have checked so far:

checked valves - intake .006 exhaust .008 (within spec, so this cant be it right?)

checked decompression weight and plunger - OK (greased just to be sure)

checked timing chain tension - OK

Took the head off and cylinder to check out the piston and pin. The pin has a little bit if extra wear on one side? The piston seems to look OK and the cylinder walls are scratch free with an even cross hatch pattern.

Also, when I shake the flywheel up and down there is a small amount of play. I can not see it move, but I can hear it. Also, the rod has slight lateral movement when I wiggle it back and forth from the left side of the motor to the right side.

Here is a video of the play in the crank, the rod and the wear on the piston and pin:

http://www.youtube.com/watch?v=Dgc0hSvIcds

Checked the oil filter and there are no signs of metal particles. Also, the stator has not metal particles stuck to it.

???

Edited by pdsage10
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my 03 does that, i think its crankshaft play, maybe crank bearings. im not sure but my 03 has been doing it for 2 years now and its still running, in fact it even made this noise after i put new crank bearings so i think part of the crank is worn and the piston is a little loose. i have seen this forum brought up many times and i have even posted it, never found or got a real answer/solution , but thats my best guess...

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i think part of the crank is worn and the piston is a little loose.

Thats what I was afraid of. Was hoping that I didnt have to replace the crank.

Gonna take the piston off and look for play.

thanks guys

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I put a new tentioner on my 03' and the noise continued. Still dont know what mine actually is either but Shawn_MC had a good point that resembles a symtom to my bike, my flywheel deffinatly had some debri in it and the crank is slightly loose in the main bearings even though the bearings are new, it moved so slightly i cant see it but i can just hear it and feel it with my hands, I mean the slightest bit. I rode my 03' for 2 years making this noise and it never broke down. Maybe im just lucky it didnt throw the crank, or maybe if can just keep running this way for a while. Who knows but its probobly not with fixing for me concidering it runs and i have a nice 08' with low cash in my pocket!

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well, my 03 makes that same noise when you grab the flywheel and move it left to right. it could be your main bearings or crankshaft, or both! you will have to split the bottom end and when you have the crank out measure out all the spects for it and if they are good reuse the crank, if they are bad get a new crank. also your uneven wear on the pin is probobly caused by that play, considering the flywheel side bearing is a pin bearing and the other is a ball bearing, one has worn out more than the other causing more play on one side therefore creating uneven wear. good luck...

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Yep, thats what I was worried about. Gonna have to split the case and replace the bearings. I really dont have the tools to do it though, so I'm considering taking the case to a shop to have it done.

Bummer.

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do it yourself!!! its worth the money youll save, there guna charge you 90 bucks an hour, one hour will pay for the tools you need witch is basically nothing if you can work around it, you can buy a flywheel puller or rig one up. its worth the expierience anyways! buy a manual and just follow the directions, i completed this proccess at the age of 15.

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Just curious, do you have any up and down play on the con-rod and how much play is there left to right on the con-rod(not side to side on the journal but how much the little end moves rocking it)? There should be very little rocking and none up and down. The up and down is what I thought your problem is. How does the piston pin fit the piston (any play)?

It's not worth it replacing the con-rod and bearings! Buy a new crank! I had the same wear on my wrist pin, almost exactly as yours.

I rebuilt my engine a few weeks ago due to rattling in the engine. Guess what... it sounds mostly the same now! Most of the noise is in the top end. Also I had play in the counterbalance shaft bearings. Installed new ones and now no play. It has less vibration but not what I feel is right. After reading allot of posts on engine noise I have come to believe these motors are just noisy!

The cam chain may need to be checked at a particular degree of rotation to remove the valves acting on the cam sprocket.

These motors are funny in that they defy logic with all the noise they produce! Never had a Honda like it.

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http://www.youtube.com/watch?v=Dgc0hSvIcds

So what do you guys think? No metal particles in the oil filter or anywhere else, but it does seem like the crank bearings are going.

Is the rod supposed to have play from side to side? Could that be the reason for the uneven wear on the pin?

You shouldnt get any movement from grabbing that flywheel and jerking on it. Id say the ball bearing is toast. The bearing behind the flywheel (roller/pin type) is going to allow it to wobble a bit and run out, but the ball bearing behind it shouldnt allow you to do that all. Unless the crank has come loose of the bearing race. But even that aint good.

That wear in the ball bearing is allowing the crank to run in an oblong on that end and thats whats wearing the wrist pin. That motion to the side is exaggerated by the length of the rod and bends the piston over sideways in the bore. These engines are pretty durable, but theyve gotta be right to live. That crank aint right.

You dont need a whole bunch of special tools to get the motor apart. A CRF specific flywheel puller is the most exotic and those things are pretty cheap.

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From what I understand the knocking noise at idle that these engines make is from the piston. The way the piston is designed (slipper piston) is what they call them, with really short skirts. That is what causes the knocking noise due to piston rocking back and forth. Also, correct me if im wrong but the right side should have no up and down play in the crank bearing, but the left side flyweel side should have a little due to the tapered roller bearing, and some in and out play but not alot. My new engine with 0 hours on it has some up and down play on the left side crank. I think if his crank was that bad you would start seeing the bronze in the oil from the small end of the rod, due to excessive side loading of the wrist pin.

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So at idle I am hearing a knocking sound (jack hammer sound).

Video:

http://www.youtube.com/watch?v=XQmG3Tpe3Wc (I am slowly rolling the throttle a bit in the video to give you an idea of how the sound changes at different RPM).

Come to think of it, I think I get this noise when my engine is under a heavy load, like going up a steep hill, or riding in a few gears to high.

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Thanks for all of the feedback guys. Really glade that I started posting on here.

I'm considering doing the work myself and buying the tools to open up the case.

Gonna need to get together a list of parts and tools to buy.

I saw that Wiseco makes a crankshaft kit with gaskets and bearings, but based on the Thumpertalk store, it is only available for 2004-2006 bikes. ?

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That wiseco kit is a really good deal, but nobody had it in stock when I needed one. Pretty sure they're made in China if that matters to you. I bought a Hotrods crank, which actally had more play in it than the one I was replacing. Pretty sure I could've changed only the bad bearing. Not too bad of a job, either.

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