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motor destroyed.

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so the motor on my 08 kx450 is wrecked. the bottom of the piston let loose, bent two valves, destroyed the cylinder, broke the connecting rod and destroyed my cases. it was a Pro-X piston with only 20hrs on it. ? is, do i just try and buy a new motor or rebuild this one. if so rebuild what parts should i use

?

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Which two valves are bent, and which side of the piston skirt is broken? Were your cams still in time when you disassembled it? I'm wondering if the chain skipped and caused all this.

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the left side of the skirt. and the two exhaust valves.

Is it the skirt below the exhaust valves, or below the intakes? If the piston hit the exh valves first, I would expect the skirt below the intakes to be damaged, based on the way it would cock in the bore.

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the cam chain is good, cams were correct. the piston broke were the rod pin goes through.

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This is the second aftermarket piston failure ive read in 10 minutes. I think i will stick with standard.

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i dont believe in aftermarket pistons.... i always buy stock... no after market company is going to beable to actually make a piston better than the stock one...

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Pro X Pistons are stock pistons, they're made in the same factory.

JE Pistons are the ones to stay away from, but anything from Wiseco or Pro X is good. CP Pistons were having problems for a while, but they should be back to the old (good) quality part now.

(Pro Circuit also sells JE Pistons as theirs)

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I've read about, and seen, way more horror stories with stock kx pistons than after market pistons. I am running a wiseco with almost 70 hours on it with zero isuues. I've also rebuilt several other kx450s with wisecos with no problems. I have however, seen many stock pistons show signs of flexing and galling the wrist pin, and even several stockers broke in half. It's insane to even consider putting a stock piston back in one of these.

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i dont believe in aftermarket pistons.... i always buy stock... no after market company is going to beable to actually make a piston better than the stock one...

That usually IS the case, but with the kx450f piston design stock doesnt cut it, too many failure stories on here with the stock breaking and then the guy getting 100 or more hrs on a std compression wiseco piston afterwards, and hey its even lighter

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I love the Wiseco PK kits.. they come with the piston, rings, wrist pin, circlips, and a top end gasket set including valve stem seals. Very convenient and the pistons are great. I do my top ends every 50 hours and my pistons have looked nearly new every time. Usually the coating on the side of the Wiseco pistons doesn't even show any wear!

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i had an 08 kx450 as well. my bike did the same thing about 4 times. i was able to contact a xtreme team green mechanic and told me the rods on some of the 2008s were machined just a tad off so when it heated up it got just a lil wiggle in it and the piston would tap the top of the crank and grenade everything... i contacted kawasaki and they told me pretty much to go f*$k myself, even though this is a common problem.

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So because of deployments and work I am now starting to build this thing back up. Here is what I have coming for it. Let me know what you guys think.

2011 bottom end complete, cases, trans etc.

2008 hot rods crank

wiesco 13.5.1 piston

hot cams stage 2

kibblewhit SS valves, springs, and bronze valve guides.

I will also be getting the head done, valve seats cut, polished and semi ported(just clean up).

also will be adding an exhaust, not sure what one yet.

what do you guys think? any thoughts something I should do. thanks

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2010 saw the new bridge box bottom piston. Does it fit earlier models without problem? I know when the 250 got the new piston the cylinder height was also changed.

The 2010 or even better the 2012 piston could be the way to go in older bikes.

I remember MXA saying that Kawasaki´s piston breaking problems was due to both piston flex as well as piston rock. As far as I´ve heard, the newer pistons solves the problem.

Edited by D-K

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So if I went with the newer piston would i have to change the cylinder? Also does anyone know of a place to get my new valve guides installed? and valve seats cut?

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If your exhaust cam is not damaged i would be interested in buying that from you. Where are you getting your head done? I need mine.. and shouldn't the place your getting your head done be able to do your valves?

Edited by Chrisj0806

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At the moment I am not sure where to get the head done. Yes the ex cam is G2G. Shoot me an offer.

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