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Motor Going Bad...

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...and man do I hate it. I must have like a 90% holeshot percentage on this bad boy. I was racing in the sand this weekend, and during the middle of the second moto I started to notice a sound coming from the engine. Still had full power, and it starts/runs normal. When I start it and its idling, you can't hear it. If I slowly roll on the throttle, a rattling sound starts to come from the top of the motor. Pulled the valve cover, and everything looks normal in there. Going in to the motor tonight to see what the problem really is.

Any thoughts on what I'm going to find?

Cracked piston?

Busted shim bucket?

Timing chain/upper gears look good.

I change the oil twice per week. Once after the race, once before. I practice 2x a week. Fresh Air filter every ride. Did not suck sand. Was not low on coolant.

Hoping its just a piston and something relativly simple to replace...

Any help would be appreciated. :excuseme:

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You can narrow down somewhat by the sound and how often. For instance, the fact that you don't hear it at idle makes me think valve train. Because a broken piston would most certainly make noise at all rpm levels and would not give you full power.

A valve may not make noise until higher rpms but you would not have full power with that either. I'm leaning towards cam chain since you have full power and no noise until higher rpms. Maybe a stretched chain or broke tensioner.

But I'm a two stroke guy, so what do I know?

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wrist pin was cracked in half

Piston looked ok. A little black stuff on the exhaust side where it looked like it was burning down the side of the piston about 1/4", but the rest looked good. No cracks. I ran the last 3 laps with it making that noise. What im wondering is should I replace the conneting rod? Gonna do the piston for sure, but since the crack was in the middle of the rod it had to be stressing the upper rod connection. There isnt a bearing like a two stroke to replace, its just pin to rod to piston. Probably try to measure it somehow. ANyway, I ran it for a million hours and never tore it down and I read about it on here so my bad.

I'm just gonna fix it and get more holeshots. :excuseme:

Going all OEM.

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wrist pin was cracked in half

ANyway, I ran it for a million hours and never tore it down

So how many hrs was it 50+ ?

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wrist pin was cracked in half

...

Oh man!!!! Did you get lucky that thing didn't grenade on you or what?!?!?!?!

Its a tough call on the connecting rod. I'd inspect it real good and look for any obvious signs of damage. If its not too expensive, I would consider just replacing it. Peace of mind and all. 3 Laps is a lifetime when running on broken goods!

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Had more like 100+ hrs on it.

Upper rod connection looks ok though. No signs of wear, no scratches, no debris. I'm tempted to run it. Gonna let a mechanic make that call though.

Yeah, glad it held up.

The same day my buddies KX250F broke off the tops of the intake valves, mashed the head and piston, took out the cylinder, and siezed the crank.

It was ugly. Bike had low hours too.

Be on the phone with the dealer this morn. Lucky they are good people.

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I was reading through this forum and just had to join after reading this subject. My KX 450 did the exact same thing. I was flying down a straight away when a loud knocking come from my motor. After pulling off and taking the valve cover off I discovered the upper cam chain rub plate was gone. After inspecting for damage, it was replaced but the knocking was still there. I ended up taking it back to my dealership where they found the wrist pin cracked. Fortunately for me, Kawi is paying for basically an entire new motor (piston, crank, rod, cylinder). I guess I wasn't the first to have this problem. I'm getting to know my dealership and the Kawi reps more than I'd like to. The second time I rode my kx one of the decompression weights on the exhaust cam came loose and shot through the valve cover. Kawi paid for all of that too! You should see if Kawi will pay for yours, they seemed happy to help me out. They never asked how many hours I put on mine. If I had to guess, around 40 hrs. When my bike isn't in the shop I love it. Handles great and has tons of power. Mine was just built on a Friday at 4 pm.

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Is there any correlation to the engine or serial numbers on the bikes that are having top end issues? Can you guys post your numbers? Has Kawasaki listed any number of bikes that need to be checked?

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I wonder why if Kawasaki knew about this problem, why did they not recall all the unsold new bikes and replace these. Or at least send a new one to the dealers who had them so they could replace them. I fear that this will happen to my bike. :excuseme:

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Yamaha just recalled the 2006 yz250f and is replacing valves for free. I think Kawasaki should go public with a statement if this really is as big of a problem as it seems to be. The very least they could do is say what serial numbers might have the weak pins...

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The last four digits on my bike's serial number are 2894. I picked it up at the beginning of January so maybe I bought it before these wrist pins became a big issue. I hope Kawi has changed the design or strength of these pins. I assumed since Kawi is paying for my repairs, it's going to be with their parts. Anyone know if the new pins have been upgraded or is this something that I'm going to have to replace every few hours to be safe?

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Is there any correlation to the engine or serial numbers on the bikes that are having top end issues? Can you guys post your numbers? Has Kawasaki listed any number of bikes that need to be checked?

You may want to read through the stickied "KX450F FAQ Thread". There are several discussions on this forum regarding this very issue and a few links can be found in the FAQ thread. It should cover everything you need to know.

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The last four digits on my bike's serial number are 2894. I picked it up at the beginning of January so maybe I bought it before these wrist pins became a big issue. I hope Kawi has changed the design or strength of these pins. I assumed since Kawi is paying for my repairs, it's going to be with their parts. Anyone know if the new pins have been upgraded or is this something that I'm going to have to replace every few hours to be safe?

Yes, wrist pin has been upgraded so if you order a new one, it will be slightly different.

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the only prob the top end had was the wrist pin wasnt it??? i had read about this earlier when ppl were have big issues with it and i was going to replace my top end before it went bad, but if it is just a wrist pin that is causing the motor to blow up, then that will definatly save me some $$$$$ although, i would like a high comp piston running around in there....

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my local dealer is taking care of all the parts. I'm doing the labor.

I've been lucky enough to ride all of the 06 450's, except the KTM (I did race an 05 KTm 450 last year though) and I have to say the Kawi is the one. They all have good and bad things about them, but this bike is an amazing machine. This wrist pin thing is a bit of a hassle, but to be able to ride a bike like this is just awesome. If you havn't done it (and you own the KXF), at least look at your pin and see if it is gauling (i think thats a word?) Pretty cheap to change the pin. Half of you guys spent $800 on exhaust, so whats a wrist pin compare to that, other then the hassle of tearing it down? The way I'm able to ride this year compared to the last 3 on the KX250 makes it worth it to me to deal with some first year blues, IMO.

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At 26 hours i installed new piston rings .the old piston was perfect to the naked eye

im sure it needed rings.but the rist pin had gaul marks runing along the length where it contacted rod & piston..the new pin seemed to have a coating that either was not on orignal or had worn away...but going over 30 hours with out service seems crazy..I feel my $800.00 pipe is a waste if i don't keep a fresh motor to work with it.

by the way my valves are still in spec. & all 26 hours are race hours my 2cents jeff

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My two cents.... I have #2269 got it on the team green demo program in October, rode or raced every weekend til late April. Tore down the top end and the piston and rings measured out fine, cylinder looked great and the piston pin didnt have any noticeable wear. Replaced with new Kawasaki parts and have about 20 hours since and all is well. I still have not required a valve adjustment. My dealership (Talladega Cycle Sales, Alabama) has sold 10 KX450F's and no one has had any problems or even needed valve adjustments. I did check my screen in January and found very little debris. I did replace my clutch plates and installed the PC springs and she is pulling hard.

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:excuseme:

Yamaha just recalled the 2006 yz250f and is replacing valves for free. I think Kawasaki should go public with a statement if this really is as big of a problem as it seems to be. The very least they could do is say what serial numbers might have the weak pins...

THE LAST FOUR OF MY NUMBER IS 1555 I BOUGHT THE BIKE OFF EBAY FROM NORTH CAROLINA I HAD MY LOCAL DEALER RUN THE SERIAL NUMBER AND HE TOLD ME IT WAS PURCHASED ON 1/28/06 IN NC.THE PROBLEM I HAD RIGHT AWAY WAS THE CAM CHAIN TENSIONER THATS ALL. I GOT LUCKY I GUESS I DON'T KNOW IF THIS WILL HELP YOU ANY BUT I JUST THOUGHT YOU SHOULD KNOW WHAT NUMBER I HAVE AND THE PROBLEMS I HAD.

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Oh man!!!! Did you get lucky that thing didn't grenade on you or what?!?!?!?! 3 Laps is a lifetime when running on broken goods!

And get this......HE WON!

Glad you made it through the weekend relatively unscathed Kawiscooter. You looked smooth as silk....as usual.

Didn't know you had ridden an '06 YZF450 already, is it too late to retract my offer? :bonk::excuseme: .

See you this weekend. Heard they are reversing Kincaid too.

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