Piston changed? KDX220

Is there any way to tell if I still have the stock pistion in my '98 KDX220 by looking in the exhaust port? I just got this bike and I have no idea what has been done to it. I would think that after 13 years it has probably had the piston changed, but is there any way to tell without removing the cylinder? If I remove the cylinder and check, should I just replace the rings or should I replace the piston too, even if it has an aftermarket pistion? Everything looks clean and I can't see any scars in the piston or cylinder. The head doesn't have any carbon build up on it as far as I can see.

When I drained the oil out of the transmission it was gray and kind of metalic looking. Is this normal (maybe from the clutches) or do I need to look for something going bad?

You can remove the head and if it's a wiseco the part number will be stamped in the top of the dome. You don't have to pull the jug just to check, although when I buy a used 2 stroke I always pull the top end completely off, clean everything, check rod and main bearings, and re-assemble with at least new rings and gaskets.

The oil was probably in there for a bit too long. The clutch contaminates it pretty quick.

You could tell something by looking through the intake side. Pull off the reed cage and look at the back of the skirt. The OEM piston has a round hole in it's skirt and an aftermarket piston will have more of an oval or round cornered rectangular hole in it.

I pulled the top end off today and measured the bore. It's about 69.055mm (2.7187 inches). What is the stock bore size? The piston looks like it's cast. Are the after market pistons forged? The head gasket was very thin. It measured .008 inch thick. Is this one of the high compression gaskets?

You could tell something by looking through the intake side. Pull off the reed cage and look at the back of the skirt. The OEM piston has a round hole in it's skirt and an aftermarket piston will have more of an oval or round cornered rectangular hole in it.

Depends on when the piston was made. I've seen earlier wiseco's with a small round hole, no hole, or a big oval hole. Seen pro-x's and stock pistons the same. That's no gaurantee at all.

69mm is the stock bore size. Aftermarket pistons are cast or forged. If it is a forged piston it't most likely a wiseco. If so, it will have a W stamped in the wrist pin boss area (underside), and a part number etched in the top.

Do yourself (and everyone else) a favor and pick up a service manual asap.

I have a service manual, but there are a lot of details that it doesn't cover. It also only covers the 200, so the bore size for my 220 was not listed.

I'm pretty sure that this is a cast piston. It has a oval shaped hole in it and a star shaped snow flake with SK cast into the skirt on the inside. Maybe it's a pro x piston. I'm going to get a Wiseco top end kit and be done with it.

Edited by big gear head

http://cgi.ebay.com/ebaymotors/Wiseco-Top-End-Rebuild-Kit-Piston-KDX220-98-05-STD-/390040214742?pt=Motorcycles_Parts_Accessories&hash=item5ad0355cd6

I got this kit ordered. It's suppose to have a Cometic gasket set with it. I also ordered the seals for the KIPS shaft from Kawasaki, so when I put it back together it should be right. The only thing I don't know is which Wiseco piston is in this kit. I've heard that there are 2 pistons and one works better than the other.

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