KX250 1999 bad piston needs rebuild

Mechanical problems discussed for Dirt Bikes and Dual Sport Bikes
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Sandblaster
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KX250 1999 bad piston needs rebuild

Post by Sandblaster » Tue Feb 17, 2015 10:30 pm

A customer came in with a bike that seized a piston.
Upon getting the bike apart we found that the cylinder was heavily ported.
I don't do much with the 250's but judging from what I see, somebody got carried away....
The customer said up until it seized it ran good.
I don't know, what do you think?
The transfers are very crude but could be cleaned up some.
kx250 99 cylinder ported 101.JPG
kx250 99 cylinder ported 101.JPG (112.38 KiB) Viewed 928 times
kx250 99 cylinder ported 102.JPG
kx250 99 cylinder ported 102.JPG (81.1 KiB) Viewed 928 times
kx250 99 cylinder ported 103.JPG
kx250 99 cylinder ported 103.JPG (91.35 KiB) Viewed 928 times
kx250 99 cylinder ported 104.JPG
kx250 99 cylinder ported 104.JPG (62.98 KiB) Viewed 928 times
If bikes are for kids I'll never grow up.

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Sandblaster
Posts: 5656
Joined: Thu Jun 07, 2012 3:50 pm
Location: Eugene, OR
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Re: KX250 1999 bad piston needs rebuild

Post by Sandblaster » Tue Feb 17, 2015 10:32 pm

kx250 99 cylinder ported 105.JPG
kx250 99 cylinder ported 105.JPG (52.17 KiB) Viewed 927 times
kx250 99 cylinder ported 106.JPG
kx250 99 cylinder ported 106.JPG (54.11 KiB) Viewed 927 times
kx250 99 cylinder ported 107.JPG
kx250 99 cylinder ported 107.JPG (50.29 KiB) Viewed 927 times
So it looks to me like they were trying to achieve more top end but went to far..
Then... they added a fly wheel weight to it...
I don't know what the port timing is but I could degree it.
If bikes are for kids I'll never grow up.

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