KIPS rattle with a new MUCH louder rattle...help me out guys (with video and pics)

[B737driver]

First off, the bike is a 2004 KDX/KX Hybrid. Was riding the other day and it developed a louder than normal "rattle" coming from either the top or bottom end. I shut it down fairly quick and got a tow back to the truck. no photos of me being towed by an orange bike were allowed .

It would start and run...but something is not right

Brought it home, washed it, and started tearing it down. I have yet to find the culprit. Piston does have some scoring on the sides. Head looks good. cylinder has very light marks (not enough to catch your fingernail on).

Which leads me to the bottom end. Rod has very little, to no up and down movement. rotating the crank I can hear very slight noises, but no metallic grinding. Seems fairly normal.

Any ideas? Thanks in advance... And MERRY CHRISTMAS!!

[B737driver]

A couple more pics...

The crank looks a little eaten up on the inner edges...hmmm is that normal?

And a look through the exhaust port at the piston before disassembly. Is the main (center) kips valve positioned correctly?

[KDXGarage]

Have you disassembled the KIPS system to check for broken subvalves?

That does sound ratlly. I would imagine checking the easiest to get to stuff first, then moving on to harder stuff.

Broken reed??

[B737driver]

reeds are good. KIPS all appear to be in good functioning shape. Wish I had something to show for comparison. It was 2x as noisy / rattly as it typically is. Even other riders in the group noticed it when we stopped for a break. I heard it then felt a slight vibration through the bars then we stopped and I shut it down. Weird thing is it was still making normal power.

What are the indications of a bad crank bearing?

[KDXGarage]

How many hours since the crank main bearings were replaced? big end bearing and rod replaced?

It is definitely noisy.

Can you take off the ignition cover and check for up and down play?

[B737driver]

The bottom end has never been split. I know because I bought the bike new in 2003. Well the bike that this motor came in. Man, 15 years ago...wow. I will pull the ignition cover tomorrow and check. Great idea thanks.

[B737driver]

pulled the ignition cover...no noticeable up and down. However, it does have a distinct squeal sound and some "clanking" when I turn it back and forth. I'll get a video of it tomorrow. Really sounds like the water pump side.

[KDXGarage]

probably time for some bearings, then!

[B737driver]

The noise appears to be coming from the water pump side. This is what I get...is it normal?

[bufftester]

No, that's not. Kind of sounds like the pump bearing on the back side of the mechanical seal, or something in the mechanical seal. Put a stethoscope on there to see if you can verify the noise is originating there. Luckily, if that is it, it's an easy and relatively cheap fix. Fingers crossed.

[Julien D]

Is it just me that thinks that piston looks like hammered hell? Something caused those gouges. Most likely a bearing in the lower end let go. Maybe wrist pin or rod bearing? There is material missing from the crank lobes as well.

[KDXGarage]

I know you said it looked OK, but can you post pics of the top of the piston?

That top edge looks very rough after I zoomed in on it.

[Julien D]

No lie. There is metal being thrown around in there and that is never a good thing.

[B737driver]

Here is the top of the Piston. All of the scarring appeared to be on the side not the top. The next photo will be of the head. It looked fine with no gouging whatsoever.

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[B737driver]

I pulled the impeller from the water pump and found that the noise was coming from the mechanical seal. Cleaned it reinstalled and that noise went away. However, the clicking sound is still there.

I then pulled the flywheel and noticed some black Gunk near the bearing. Unfortunately, this had metal in it. They were very fine shavings on the flywheel side of the seal.

I guess it's possible through the combustion process that these shavings are what scored the piston. I also had a minor leak at the air boot/carb that was allowing some unfiltered "stuff" in. Not excessive but there was a little dirt on the inside of the carb intake.

The plan is to rebuild the bottom end and hope to get another 15 years out of it.

I'll get a few more pics when I get back home.

[KDXGarage]

I think I am about to retire from the guessing game on the internet.

Did you happen to take any pictures of the black gunk you speak of?

If you think you had dirt get in, how are the cylinder walls?

Any cylinder wall pictures??

How many hours on the engine since the last top end? Did you clean the inside of the head before the picture was taken? It looks extremely carbon free for a head.

[B737driver]

Sorry man I’m on the road and not at home to take pictures. I did take a pic of the black gunk (looks like the stuff you get on a magnetic drain plug) but when I try to upload the attachment is too large. The top end has about 25 hours. I did not clean the head before the pic...surprised me too. The cylinder wall is amazingly clean as well. Still has the cross hatch but has some vertical marks, not enough to catch your fingernail on.

I too am playing the guessing game. I think the culprit will reveal itself when the cases are split.

Thanks for the help. Really was hoping to find something without tearing into the bottom end.

[KDXGarage]

Ah, it's not about the lack of pics. No worries.

Any chance the oil is weeping from the steel insets in the case half? I know the E models had that issue. I don't know where the metal would come from, though.

Any detonation on the edge of the piston?

[B737driver]

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Here is the "gunk".

[B737driver]

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Cylinder... again, there are marks but no scoring.