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I got a 98 KDX220 a few weeks ago from a guy who said he had just replaced the piston with a wiseco one. I rode it around the block and it seem good. Once I got it home I rode around the block and it rode good (about two miles) then died while riding and wouldnt start. I pulled the carb to clean and then the reeds to inspect. The reeds looked like they had metal shavings in them… So i looked down in where the reeds had been and could see the back of the piston and it looked awful (see attached image) what could have caused this? I guess Im gonna pull the top end and see what it looks like. Will I need to split the cases to remove metal shaving?

Wow! That looks horrible. Take the top end off & take more pictures.

It is zwo stroke… i dont think u need to split the case

If you have any shavings down in the bottom end (likely) then you should split them to properly clean and also check/replace the mains and seals. Being a new to you bike with a top end that just appeared to let go, better to have the peace of mind from doing a through tear down/inspection/rebuild. It is not hard and can be done with very few special tools, especially if you are handy with a wrench.

ahh man, that is a bummer for sure! I had the same thing happen to me. I bought a 220 from someone who said it had a new piston in it. Rode it for a short time and the piston skirt let loose, locking it up. The stock cast pistons on the 220's are known for that, it needs replaced with a forged one, like a Wiseco. When it happened to me, I had to replace the head and I sent the cylinder to Millenium Technologies to repair and replate.

I did split the cases for peace of mind. It really wasn't that bad. In this day and age, you know someone has documented how to do it on the internet, making it even easier: viewtopic.php?f=77&t=12241&hilit=splitting+cases

Sorry for your luck! But its definitely fixable

This is my first time trying to rebuild a bike so any advice helps! I took the cylinder off and found some interesting things, I will attach some pictures. It looks like one of the wrist pin clips fell out and caused a bunch of damage… I found the bent up clip down by the crank once i pulled the cylinder, you can see where it was in the attached pictures. I’m probably going to send the cylinder to powerseal usa, it seems like this is the best option. Im not sure what to do about the cylinder head though, it has lots of pitting, Im assuming this is from the metal shards bouncing around. Anyone have advice on what do about the head, can it be repaired? Looks like ill be spitting the case on my first rebuild as well haha. Thanks for the help!

Tyl3r, thanks for the comment I think I posted again right when you replied. Sounds like I need to look for a new head! Also I’ll check out millennium technologies! Im glad there’s plenty of documentation on these bikes here, I’ll will be studying up on splitting the case haha!

Ah hah, so they did replace the piston... just didn't get the wristpin in there right, bummer.

I was trying to get a RB-Designs modified head when I was putting mine back together, he told me mine couldn't be saved and I needed a new one, it looked a lot worse than yours though. Could send him an e-mail to see what he thinks or ask the place that repairs your cylinder for their opinion.

Ouch. Yep, typical circlip failure. The big worry is that where are all those little pieces? My bet is in your main bearings and, even if they're not still there, have probably caused damaged to them. IMO I would be splitting the cases and doing a complete crank/rod overhaul and new crank bearings seals.

At least its not this bad: viewtopic.php?p=178350#p178350

I'm with SS109, I'd do the same.