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Kx250f 2011 shit the bed! - with video


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Was riding at my mates flat track last friday and i killed my bike.

now the conrod has snapped but not all the way threw only on one side, and the piston has then come up higher then it normally would and smashed the exhaust valves, destroying the exhaust buckets, exhaust cam and retainers etc.

now the cylinder is toast, the piston is not going to be resused, the conrod is snapped, guessing fair amount of damage to the bottom end in general.

so im currently looking at my options

parts list so far is

 

piston

cylinder

bottom end or repair current one with new conrod and bearing etc

 

iv ordered a brand new cylinder head with new exhaust valves and springs, lifter buckets.

the inlet valves on my old head are past their servicable life anyway and need to be replaced.

 

so what should i do?

 

im thinking along the lines of going a hotrods crank kit for about $500-$550 landed in aus

a cylinder works 269cc piston and cylinder kit 

and at very least a new exhaust cam and inlet gear.

is it worth putting after market cams in?

will the ecu run the 269cc engine allright?

 

any ideas or suggestions would be great...

 

 

Edited by crackhead
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I've repaired Kaw cases with much worse damage. I also have a good welder fab guy.

 

I bought and rebuilt 2, 2011's within this year with rods through the cases. One I rebuilt with a 269 big bore.

There seems to be something special about the 2011' and snapping the rods.

 

this pic below is from a 2014. These cases were not repairable

 

 

 

 

0717141341.jpg

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I've repaired Kaw cases with much worse damage. I also have a good welder fab guy.

 

I bought and rebuilt 2, 2011's within this year with rods through the cases. One I rebuilt with a 269 big bore.

There seems to be something special about the 2011' and snapping the rods.

 

this pic below is from a 2014. These cases were not repairable

Have you found any indication of why the rods snapped ?

 

The the piston sieze on the pin or the main bearings sieze ?

 

Wonder if they changed the rods for 2012 

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Have you found any indication of why the rods snapped ?

 

The the piston sieze on the pin or the main bearings sieze ?

 

Wonder if they changed the rods for 2012 

 

my engine builder said too many hours on a small high performance engine.

the motorbike shop that i use to source parts, said his built 3 2011's with the exact same issue, snapped rods, and said it could have been alot worse.

nothing was sieze everything still moves quite freely.

it would have been one of the needle bearings dislodging and getting jammed in there, then hyperextending the conrod and piston up into the exhaust valves.

 

on an interesting side note i found one of the piston pin snap rigs down in the case aswel... not sure how it managed to remove its self...

Edited by crackhead
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KX250AF conversion. :ride:

 

already riding a  rm250 06 as well, more then likely look for a 2013 450 or maybe an old cr125 or something once i sell this thing.

ill get it repaired all spot on and sell it, it was actually for sale when i broke it last friday i had a guy coming to look at it that night.

 

dropped it off tonight to get the cases repaired, ill order the replacement parts once some people pay some of their dam bills.

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Have you found any indication of why the rods snapped ?

 

The the piston sieze on the pin or the main bearings sieze ?

 

Wonder if they changed the rods for 2012 

 

The only thing I can come up with is metal fatigue similar to what Crackhead said.

None of the bikes we've repaired came with hour meters so there's no way to know how many hours is too much,

We  don't own any of these we just repair them.

We've found Honda's will launch the lower rod bearing when run at the limit, if pushed much beyond 35 hours so it might be a similar thing with the Kaw's

 

I haven't seen any instances of the piston pin seizing on the rod unless the pin was bent due to piston contact or a burr on the cir clip seat. 

 

Also never seen the main bearings seize. We've seen the lower rod bearing seize if thats what you refer to...

Edited by nesc103y
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The only thing I can come up with is metal fatigue similar to what Crackhead said.

None of the bikes we've repaired came with hour meters so there's no way to know how many hours is too much,

We  don't own any of these we just repair them.

We've found Honda's will launch the lower rod bearing when run at the limit, if pushed much beyond 35 hours so it might be a similar thing with the Kaw's

 

I haven't seen any instances of the piston pin seizing on the rod unless the pin was bent due to piston contact or a burr on the cir clip seat. 

 

Also never seen the main bearings seize. We've seen the lower rod bearing seize if thats what you refer to...

 

Meant big end not mains , thanks 

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What kind of riding do you do ?

 

Do you ride the bike on the limiter ?

 

What oil do you use and how often do you change it ?

 

 

85 hours is not that much for a bottom end if not raced.  

 

I agree but why buy a race bike if its not going to be raced.

there are alternatives

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yeah learnt how to ride on it with about 20 hours, only been the last 30 or so that its actually been given any hell

hasnt come close to any type of hardwork bar the last 10 or so hours at my mates flat track where its been getting a pasting 

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I agree but why buy a race bike if its not going to be raced.

there are alternatives

 

Ok so i raced for the last 8 years now i ride Mx tracks for fun so what do you suggest i get, a crf 230 ?

 

Not even 1% of mx bikes sold are actually raced.  

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