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Kx250 namura piston

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Hello just picked up a 2004 kx250 that blown up. Just looked at the piston and sure enough it’s a namura piston. These thingIMG_1510610771.408546.jpgIMG_1510610827.984287.jpgs are prone to exploding to destroying engines to I️ would highly recommend not buying them even though they are cheap. That’s exactly why they blow up bc they are $60 and terrible quality.

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Thank you for sharing the photos. Wouldn’t you agree that the piston seems to have held up quite well by not throwing a skirt, considering how badly cracked it is? If the skirt had actually gone, your barrel or bottom-end wouldn’t be in as great a condition as it is. If anything, the piston holding together the way it has, saved you a lot more time and money in my opinion. Maybe the brand isn’t so bad after all? I’ve never used one, so can’t pass judgement. Also, how many hours are on that piston?

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Yeah I’m definitely gonna need to hone the cylinder but even though the head is dinged up I’ll still use it but might have lower compression

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How's the thrust washers (edited)? Ive also seen the Big end bearing starting to frag with no noticeable up or down play too ...I've personally ran namuras on all of my 2t bikes for a few years....ZERO issues. 

Edited by argclh6670
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I've personally ran namuras on all of my 2t bikes for a few years....ZERO issues. 


This is what I’m talking about, long-term use experience of the so called “bad quality” piston, but with no experience of failure.

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Yeah I’m definitely gonna need to hone the cylinder


I always thought it was a bad idea to hone Nikasil plated cylinders?

Also, besides the more obvious reasons, the pitting your parts have can also be due to coolant leaking into the cylinder and eroding them. Make sure you check your barrel closely for any kind of damage in water channel areas.

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My local kawi dealer said it was fine.


That’s good news!

I threw a skirt on my last piston, so wasn’t as lucky as you. It was the piston the bike came with when I bought it, and I was dumb enough to ride it a few times before doing the top-end.

Did you dealer say the honing was Ok to do? Or just that the barrel was not compromised?

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Yeah it’s a little scratched up but no deep gouges so they said they could hone it to get all of them out


Be gentle with it, so you don’t go out of spec on your tolerances.

You need to make sure your compression, jetting, and timing are all within spec once you’ve finished your repairs, because on closer inspection of your photos it looks like the damage to your piston crown and head is actually due to pre-ignition (detonation).

Get the whole engine repaired and get all the above mentioned settings back to stock before running it in and/or riding. Obviously the jetting needs to be set to your weather/altitude etc.

Please don’t ignore any of this, or you’ll be blowing another piston very quickly.

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