NEED HELP! Cylinder issues!

[Xtremesports445]

I have an 02 kx 125 that I bought used about 9 monthes ago and i am currently in the process of doing my first top end. I took it apart and found out that my engine was already bored and i didn't know it. there is also some fairly bad scoring on the piston and cylinder. on the piston, where the 2 little holes are (i believe they're for lubrication). on both sides of those holes there are huge gough marks running all the way from top to bottom on the piston. they are very easily felt. there is also some scoring in the cylinder in the same place where the exhaust bridge is. I'm guessing that i need to replate it? And what caused these problems in the first place? thanks for ur help.

 

[76GMC1500]

Does it have an iron sleeve or is it currently plated? Bored cylinders are usually have iron liners. If the liner is sufficiently thick, you can just have it bored again, usually $60-90. Throw a new piston in there and everything will be like new. Otherwise, you'll have to send the cylinder out to be replated (closer to $200).

 

[john stu]

if it needs to be plated send it to eric gorr and get a big bore 144 setup!

 

[Xtremesports445]

if a magnent sticks to it that means it is an iron sleeve right?

 

[RM_guy]

if a magnent sticks to it that means it is an iron sleeve right?

Yep!

 

[Xtremesports445]

alright, so if my lining is thick enough, i can just have it rebored? And also, how come my piston got so badly scored from the exhaust bridge? is it something i need to worry about or will it get fixed once i get my cylinder bored/replated?

 

[earl pittz]

You will probably want to get a new piston. I think you can rebore it but you will have to get it replated. I personaly would get a new sleeve.

 

[snb73]

Is the cylinder sleeved?

 

[Xtremesports445]

You will probably want to get a new piston. I think you can rebore it but you will have to get it replated. I personaly would get a new sleeve.

i'm confused. are you saying that i won't be able to get it rebored without getting it replated first? is their a difference between getting a cylinder replated and getting a new sleeve? please help me out, right now i look like this :coocoo:

 

[Xtremesports445]

Is the cylinder sleeved?

as far as i know, it seems to have an iron sleeve in it that has been bored out to dimensions that i will have to get measured soon (probably this weekend)

 

[snb73]

Why someone would sleeve a 2002 cylinder when replating costs about the same, is beyond me. There is a reason factories use NICOM coated cyliders and not steel sleeves anymore. I would suggest getting the bike back to stock form. Call Eric, he may have something servicable for you to use. If your cylinder is useful, you might get some credit for it. E*ay is an option too.

http://www.forwardmotion.com.mx/

 

[Xtremesports445]

snb73, that's what i was starting to think too. isn't it true that sleeves wear out faster than coated cylinders? i'll take it to my local shop this weekend and have them look at it/measure it and i'll probably decide what to do from there.

 

[76GMC1500]

Change your right side crankcase seal while your bike is down, it doesn't take but few minutes to do and a leaking right side seal can cause scoring over the exhaust bridge. Don't forget to drill the oil holes in your piston.

 

[earl pittz]

I didn't know you could drill your own oil holes. Do you just drill it and then smooth out the burrs and edges?

 

[snb73]

Here is a link to U.S. Chrome, follow the link to NICOM and they explain the hardness levels. The short answer is NICOM is more durable (harder) than steel. You can have years of service and top end replacements from a NICOM cylinder without needing to replate/bore it. Where as a steel cylinder, over the same period of time, could need multiple bores and stepping up piston sizes.

Good luck, Steve.

 

[Xtremesports445]

76GMC1500- how do i get to the right side crankcase seal?

 

[Xtremesports445]

update

So I took my cylinder to my shop on saturday. After the guy just looked at the cylinder, he said it was good enough that i could just throw a new piston in and be okay. However, he also said that it was bad enough to where i could have it replated. So now i'm wondering what to do. I'm worried that it could cause more issues down the road if i don't fix it now. One questionable thing that he said was that the cylinder didn't have a sleeve in it. But then how come a magnet sticks to it? How could he have known just by looking? Also, it has been bored out to 134. (surprising, because the bike didn't have a whole lot of power). he also said that the scoring up and down the exhaust bridge and on my piston (the piston has actual indentations up and down and on the ring) was due to overheating (instead of crankcase seal), which i believe is probably correct because my piston pin was warped. so if i just put a new piston in, wouldn't it begin to score again very quickly? Also, i researched a bit and it sounds like a warped piston pin is pretty uncommon and is therefore a sign of fairly serious over heating, no? i want my engine to run good again and i want this done right. so should i just send it to eric, or is it not as serious as i think? (all of important questions are in bold) Sorry for such a long post

 

[elcamino12sec]

If it has an iron cylinder I would just bore it to the next size to clean all the scoring, this will make it like new again. Then get a new piston, pin, pin bearing, clips, rings and gaskets, clean the power valves out and you will be good to go like brand new again. I never see why folks are so againts boaring an iron sleeve, it only cost like 50-75 dollars and that is way less then coating a cylinder. An iron sleeve is made to be bored once it is gets scored. Once you score a plated cylinder the only way to fix it is to plate it again. If you do bore it, make sure you bring your new piston to the machine shop before he bores it, this is VERY important. Your machine shop guy will tell you what the next size over bore you will need.

 

[Xtremesports445]

i'm still not even sure if my cylinde is plated or has a sleeve. (i know i already asked this question, but the guy at my shop said it didn't have a sleeve) So, just to make things clear, if a magnent sticks to my cylinder wall, then the only possible thing it has is an iron sleeve, right?
thanks

 

[snb73]

If you can, take a few pictures of the cylinder and post them. Take some from the top, looking down. Take some of the scoreing.

If you mechanic is a graduate of MMI, then I would be inclined to trust his opinion. I think the NICOM coating is magnetic, hopefully someone more knowledgable will chime in.

From U.S. Chromes' site,"Nickel Silicon Carbide composite coating. NiCom® is an electroplated nickel matrix with hard particles, of SiC, uniformly dispersed throughout the coating."

Give Eric a call and ask for his guidence. He won't steer you wrong. If you want it done right, send it to him. If it is in specs, he'll tell you. If you go that route, have him send you a top end kit with the correct piston. I'd suggest a WIESCO forged one.