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sad 97 kx story; need opinions.

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So about 5 months ago I bought a beat up old 97 kx125. It was run into the ground pretty bad, but I got it for next to nothing, and I had one when I was younger, so I grabbed it. I stripped it down to the frame and started my rebuild. The bottom end of the motor seemed to be in good shape, and the rod had no play in it, so I replaced a couple seals and called the bottom good. Every single other part of the bike was rebuilt/restored/replaced. She looked awesome and ran even better.

On my third ride(at about 13 hours) it started making some weird noises, so I coasted where I could, and rode slow and easy where I couldn't just to get home. Once I was home, I called my buddy over that builds two strokes in his sleep, so he could hear it. After ten seconds of running it seized. We take it apart And see that one of the bottom rod bearings got into the top. So my crank/rod is froze, and my cylinder/cylinder head, and piston are now garbage. So I have a completely rebuilt bike sitting in my garage with a junk motor. What should I do? Try to salvage it? Look for a beat up bike with a good motor for cheap? Will a 250 fit? Throw me some thoughts. Thanks for reading.

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That's probably what I'll do. I can't find a new crank but everyone says I can repair my old one. I have found a few decent looking top end parts on ebay. I guess I'm asking if I have any other options on motors since I'm basically starting from scratch anyway. Will a 250 fit in my frame? How new can a different 125 be, and still be compatible?

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Rebuild the 125. There are still lots of bikes and parts out there for this generation on Craigslist and Ebay  ( http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR3.TRC1.A0.H0.Xkx+125+crank&_nkw=kx+125+crank&_sacat=0&_from=R40  ) as well as shopping around the forums. I have a modified cylinder for a 95 on a shelf in my garage for example.

 

 

ps: the 93 was the best running 125 engine of the 90s models if you're looking for parts.

Edited by OldMechanik

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"it started making some weird noises, so I coasted where I could, and rode slow and easy where I couldn't just to get home"

That statement is used all to often here, normal after someones bike goes pop.

Next time you'll know not to ride it after it starts making nosie.

As for what to do rebuild it. How bad is the jug? You should just send it out and get it re-plated, get a new head, top end kit, bearings and seals, and have the crank rebuilt.

Edited by moose_338

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I'm definitely kicking myself for riding it home. As for the top end; it's completely toasted. Wish I had pics, but I'm working out of town. There's a 3/16-1/4 inch groove from bdc to tdc with a needle bearing neatly welded to tdc of jug. Head and piston played with it before the jug got it. Looks like a grenade went off in there.

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I guess it's more like 1/16-1/8 inch groove. Just seems like more when you're looking at something like a cylinder wall, lol.

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first off a 250 will not fit with minor adjustments, you will have to cut the cradle and rebuild it, I wouldn't do that.  You spent a good amount of time and effort to restore it, I would get the cylinder repaired, there are many companies that do it, they may be able to fix the head as well, and go through the bottom end with new crank, bearings and seals, then you know what you have.

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Why not bore it out then an make It a big bore instead go read on gorr's website the tuning guide it will give you some in site to what jugs fit that era. the risk with a used cylinder is the plating maybe worn out all ready and you'll have to replate it anyways and exspense. If ya send it to like gorr and the big bore kit includes the replating as part of it. Check and see what kind of big bore pistons are aavail for it from like wiseco and wossner get a new crank = kx some pics would help before ya just go and write off the cylinder you have now. YouR buddy sucks i would of told ya to not even start the bike again damage was done All ready.

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As far as not starting it again, it didn't sound as bad as you'd think for what damage occurred, and I just rode it 6-7 miles. In hindsight I should have had somebody get a tow strap and come back and get me, and not start it at all. As far as the 250 idea goes, I did some more research and as someone already stated, it'd be a pain. I plan on rebuilding the 125, just not sure about my parts. How much overbore can the stock jug take? I've read that after to much, the ports won't work because they are at an angle, and end up being in the wrong spot. Am I on the right track? I'm guessing this is why most big bore kits have a new cylinder. Thanks for the replies guys. I'll be home Sunday or Monday and I'll take some pics.

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Finally back at it. Think I'll send my top end out for a repair/overbore. Forward motion seems to do a pretty complete job for 500, and some change. What do you guys think? Then I'll try to find someone local for the bottom end.

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I'm thinking a 144 kit would be cool, just have to figure out how much it has to be bored out to repair the damage done. I'll probably go with the smallest one I can get away with.

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