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cylinder help..pls..pls kxf 250

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This topic has been covered in previous posts but I am not able to determine a clear cut plan of action due to conflicting opinions.

Bike: 2010 kx250f

I am not sure whether to attempt to deglaze my cylinder with a scotchbrite pad as some say that this is a good method and others say this will damage the nickasil on the cylinder (a local mechanic says NEVER to do so as the cylinder will be damaged).

This is the second ring change (first was with the piston), the cross hatch marks are not visible where the ring comes in contact with the cylinder wall but underneath that point there are cross hatch marks.

The first piston change I did not deglaze and it seemed as the ring did not seal properly as there was less compression and black exhaust smoke on warm ups.

Please if an experienced mechanic could give a conclusive answer to this subject!!

HELP I NEED TO RIDE!!!

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If I am to use a scotchbrite pad, what kind of pad, green, red??

dry or with wd-40??

I assume following the 35 degree angle rule?

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my names dave and i build motors for a living. you can use scotch brite and get away with it but it doesnt leave a big enough plateau in the nikasil and wont give you as good a ring seal. the best way to do it is to use a diamond flex hone. the diamond carbide in the tips of the hone are the only things hard enough to leave a substantial plateau that will hold more oil and give you better ring seal. go to rockmountainatvmc.com and look up the hones in the tools section. you want to use the smallest possible hone for your cylinder. they carry a 77-83 mm flex hone. part number 1284240007. you want a good 35-40 degree cross hatch on the cylinder. build it dry and break it in quick and hard. you only have about 20 seconds to get those rings seated so start it up, make sure nothing is leaking or messed up, kill it, take it out to the street and immidiately after starting do a 3rd gear start. you wanna put the motor under as heavy a load as possible to ensure good ring seal. pm me if you have any more questions

hope this helps

Dave

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o and dont forget to coat the cylinder and hone with WD or some type of cutting oil

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Always deglaze. I'm not sure why the myth that it will damage the cylinder still exhists. I prefer a ball or brush-type hone usually, silicon carbide, scotchbrite is not aggressive enough but is better that nothing. A better by-hand choice is 320-400 grit wet sandpaper but a hone is way easier to do a uniform job.

Always hone wet, and clean it well with warm soapy water, then contact cleaner and a white cloth, then oil with clean white lintfree cloth with your choice of oil.

Always deglaze, always wet. I disagree with the dry rebuild but that isn't your question anyway.

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I disagree with the dry rebuild but that isn't your question anyway.
So do I. I concur with the rest of your post as well. 320 grit Flex-Hone, usually aluminum oxide grit. Tungsten Carbide is OK, but you need to be more careful with it.

Finish cleaning up with a rag wet with ATF :smirk:

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Thank you Dave and everyone else!!

I have to try to find the flex hone in Greece(probably impossible), this is why I was avoiding this process and preferred to stick to the simple scotchbrite/sandpaper method.

At least now I know I must deglaze...

and my cylinder will not be damaged...

Best regards,

Nik

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