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Discussion Starter #1
I have an 09 KX85 that had about 22hrs on it when it quit. I pulled engine apart and found RH wrist pin clip a piece about1/4 in long broke off and damged piston and cyl rest of clip was still in groove. So installed new piston and jug engine run for about 14hrs and quit again. Pulled eng apart and found exact same thing happened again RH wrist pin clip chunk broke out damaging cyl and piston. looks like there was end play in wrist pin i measured approx .015in. measured different pin lengths were all about .003-.005 in difference. Looking for some help determining what would keep causing this as it happened even when the bike was new out of box. Faulty parts?. also have always used OEM parts.
 

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Dirt Bike Dad
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you could try a different brand wrist pin.
I would take it to the dealer and ask them. You can also email your country Kawasaki for help, depending on what country you live (Aus Kawasaki is very helpful)
Ive never heard of this happening twice in a row before.
 

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Discussion Starter #4
i talked to my local dealer about it but i dont think they know anymore than me. I live in canada so i will try calling kawi canada. I havent done anything different than i have in the past as i usally do top end about every 20-25hrs because we race. The only thing i have noticed on the 2 pistons is on the RH side that fails the clip groove you can see is visually a bit deeper at the top than the new one i put in. i have reassembled eng and will probably pull apart at 10hrs.

thanks for the info
 

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Discussion Starter #6
It is a 12 yr old boy who rides it tapped but there is lots of kawi 85's been raced the same way, they are generally bullet proof. One thing i noticed and the only thing i can see is on both failed pistons both on the RH side the upper part of clip groove is noticably deeper than the LH side and even compared to a new one iam not sure if it is pounded out or not.
 

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maybe the orginal piston is a little bit differnt then what your running ive herd of someone with a kx80 who had to auctually drill two small holes in the piston below the rings. im no expert but maybe its something similar. there has to be an explination as to why its happend twice. keep us updated if u find any news
 

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Discussion Starter #8
yes, piston should have 2 small holes on front exh side, slotted hole at back for intake side. i measured piston dia. and cly to piston clearence all with in spec. I will let you know whats happening and thanks for the input.
 

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Knows more than he needs
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could it possibly be that your connecting rod is stretched/twisted or contorted in any way? maybe when you get a chance you could measure your connecting rod and see if its in spec and maybe theres a bad bearing somewhere thats allowing the piston to move cockeyed. just a thought. best of luck!
 

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My hat is made of tinfoil
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Try a Wiseco instead.
Warm the bike up some before ripping on it too hard is all you need to do and a wiseco will be a lot better than the stock crap.
 

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Discussion Starter #11
Yes i have looked at buying a wiseco I keep her different things on them as well i have always had good luck with OEM parts in the past and that why i have used them. I went back to my dealer with my pistons and talked to the kawi mechanics and they felt it could be just on the border of being lean as where the wash marks were on the top of piston. They also could seen what i did the RH clip groove was wearing deeper which they thought hi RPM & heat could do. just a theory at this point. I am running a 135 main jet which is what i ran in last years bike and 22hrs of this years bike ( blew up , then agin after 12hrs). the only difference is my son is starting to ring its neck a lot more this year. I am going to go back to 140 main jet then try a 137 main and inspect piston and see what things look like. the other suggestion that came was fuel brand. I dont know about US but canada everyone has felt our fuel quality has gotten poorer and more ethanol added. The dealer said they had some of there snowmobiles blowing up and they started mixing 25% race fuel and it seemed to help out with quality and cooling. So i will do some more expermenting and let you know how it goes.
 

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My hat is made of tinfoil
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Yes i have looked at buying a wiseco I keep her different things on them as well i have always had good luck with OEM parts in the past and that why i have used them. I went back to my dealer with my pistons and talked to the kawi mechanics and they felt it could be just on the border of being lean as where the wash marks were on the top of piston. They also could seen what i did the RH clip groove was wearing deeper which they thought hi RPM & heat could do. just a theory at this point. I am running a 135 main jet which is what i ran in last years bike and 22hrs of this years bike ( blew up , then agin after 12hrs). the only difference is my son is starting to ring its neck a lot more this year. I am going to go back to 140 main jet then try a 137 main and inspect piston and see what things look like. the other suggestion that came was fuel brand. I dont know about US but canada everyone has felt our fuel quality has gotten poorer and more ethanol added. The dealer said they had some of there snowmobiles blowing up and they started mixing 25% race fuel and it seemed to help out with quality and cooling. So i will do some more expermenting and let you know how it goes.
I only use chevron, esso or petrocananda gasoline, the other barands make my bikes, trucks etc. run badly.
 
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