Joshawajc

I've got an 02 KX 125 and I thought it runs good.. Friend bought a Suzuki 125 and mine WAS faster. He had a new piston put in, and its a totaly different bike. Pulls up front wheel in every gear. Now mine feels very weak next to his. Should I put a new piston in or what do y'all think?

gscx

well if youve never put a new piston in you should probably get around to it in the near future

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2004 YZ-125 - PC exhaust, Blue applied triple tree, blue turner OV bars, ASV levers, Sunline sprocket and gold chain, FC springs, white plastic .
DONT MESS WITH ME, I HAVE A HAMMER AND WILL USE IT!!!!!

wr250f95

being an 02 and a 125 your due for a top end.
http://www.mototips.com/how-s-perfor...html#post35760

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turtlemann14

did he get the piston enlarged? iow changed the bore size?

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gscx

if you go awhile before changing the top end it will feel alot stronger when you put it in and ride it again

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2004 YZ-125 - PC exhaust, Blue applied triple tree, blue turner OV bars, ASV levers, Sunline sprocket and gold chain, FC springs, white plastic .
DONT MESS WITH ME, I HAVE A HAMMER AND WILL USE IT!!!!!

Joshawajc

I dont think he had it bored out. The new piston may have been a little bigger. Can I do this myself ? How do I smooth the sides of the cylinder? I have not been into a dirtbike before.. Whats the best "how-to" out there?

JThompson

of course you can do it yourself
http://www.mototips.com/how-s-perfor...html#post35721

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gscx

the piston was the same size, if he didnt bore it out and he tried to put a bigger piston in it it wouldnt fit obviously. and if its an 02 and you ride it hard alot you should check your plating in the cylinder to make sure it hasnt worn through. but use a honer to put a crosshatch patern in the cylinder before you put a new piston in

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2004 YZ-125 - PC exhaust, Blue applied triple tree, blue turner OV bars, ASV levers, Sunline sprocket and gold chain, FC springs, white plastic .
DONT MESS WITH ME, I HAVE A HAMMER AND WILL USE IT!!!!!

Joshawajc

Obviously I do not know much about this, but what you say makes good common sense. You say to use a honer to make crosshatch pattern. Where do I get a "honer", and what is a crosshatch pattern? Also, what is the purpose of replacing piston, instead of just smoothing the cylinder walls?

gscx

i would check ACE. ask one of the people there where you can get a honer that can fit in a small cylinder, you need a drill to use it. then ask him how to use it. when you use it a crosshatch looking patteren will form in the plating. you replace a piston because over time the sharp edges on the top of it will get rounded over and you will lose compression this way, also you replace the ring at the same time, and the same thing happens to this, the sharp edges get rounded over resulting in lower compression. also, it is pretty hard on a psiton that pulls 12 grand regularly. if you leave it in there too long it can shatter=FAIL. so, just replace it, or you can take it too a shop to get it honed out

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2004 YZ-125 - PC exhaust, Blue applied triple tree, blue turner OV bars, ASV levers, Sunline sprocket and gold chain, FC springs, white plastic .
DONT MESS WITH ME, I HAVE A HAMMER AND WILL USE IT!!!!!