Your piston looks like there might be a problem, but the case is fixable with a little JB Weld. Is that from a KDX220? It looks like this wasn't the first time the cases were split. And what's with the sluge in the corner where your thumb is pointing to?
BTW you either have a rat infestation problem or you got your thumb stuck in the vise grips. :scream:
Yeh like the skirts off the piston are missing they shattered off down into the crankcase blowing that hole in the case. That sludge, would be a mixture of oil and bits of piston, unless your talking about the whitish sealant. I have some alluminum welding rods you use with a propane torch which welding that back in place and sealing some cracks is todays project. The cylinder wall is amazing not scarred, however the ports have been chipped away at im going to take a dremel and smooth the inside of them out where they have been damaged. Clean the KIPS, and i guess its time to replace seals while i have it cracked and a full gasket kit, and obviously piston kit.
im not positive but i roughly measured the piston at 68.6562mm, which would leave me to beleive its the stock 69mm bore, as far if its an oem piston i dont know of any identifying marks or anything to tell. On the top of the piston theres a B, and an arrow, on the remaining inside of the piston theres a number 2, and what looks like used to be kind of a star that might of said OK in it but i have no idea.
Well tonto, you are not the first to own a KDX220 that had it's skirt blown up. It seems that this is a known problem. I feel lucky that I found DRN and read about this possibility before this happened to me and I put in a Wiseco piston immediately after getting my bike home. This should be a warning to other KDX220 owners, for sure. Do you attribute the problem to anything specific that you are aware of, or are you just another of the victims who got caught with a bad piston from the factory?
Iv had a unfixable problem jetting this bike since iv had it (excessivly rich/burning oil) which im sure is because of oil leaking into the crankcase now, back then it might of just been a seal, or maybe the case was already cracked some. I shouldnt have neglected to tear the topend off at least. Im sure i would of found at least cracks in the piston if not already some major damage and could have prevented the large hole in my case. My beleif is it is an oem piston. The previous owner was supposivly an old man but that didnt mean he didnt have a son who went and ran it WOT on a straightaway all the time or something. The topend isnt hard to tear off to inspect, and a wiseco piston kit is only 75$ and 20$ for a topend gasket kit, a new case will cost you at least 360$, and the time of splitting, disassembling, and reassembling with a new case is time consuming. If you have any concern about it, dont procrastinate like i did. Only wish i had knew about the oem pistons beforehand.
The problem with the OEM pistons can be seen by simply looking inside one of them around the transfer port. These are cast and the metallurgy is just like KDX clutch parts --crude & unfinished. There's a number of sharp metal edges & angles [read 0 radius] that are just fractures waiting to happen. There seems to be no consistency in parts from bike to bike --some worse or better than others so probably the worst ones are failing. If you absolutely have to use the OEM piston, take either a round file or a dremel and smooth out those casting irregularities inside the piston --get a nice smooth even finish, then finish with some 320 wet or dry paper.